First things first   Sometimes the easiest method for fixing a standalone license is to simply activate the same license again. No need to return first. Just get the full activation ID for any broken licenses and activate them again.   Look for the broken licenses within FlexSim by going to Help > License Activation > View Licenses tab and pressing the View Licenses button. Scan the license information for licenses that indicate they are **BROKEN**. For licenses that are broken, look up the full activation IDs in your online FlexSim Account. Using the full activation IDs for each broken license, activate the licenses normally within FlexSim by going to the Activate tab and pasting and activating each activation ID in turn. No need to return the licenses first. In case you need more detailed activation instructions, see: Standalone - Activation - Online Standalone - Activation - XML / Offline   If you completed the 3 steps above but encountered error messages, it is time to manually repair your licenses.   Okay, time to repair   Standalone licensing does not have a method for repairing online. Here are the steps to manually repair your license. These instructions apply to FlexSim 2016 and later. If you are using an older version of FlexSim, please download FlexSim's latest version and follow these instructions. You can manage your older FlexSim licenses from the latest software - the License Activation window will still show your older licenses and you'll be able to complete all these steps for your broken pre-version-16.0 licenses.   Open FlexSim as an administrator by right clicking the program icon and selecting Run as Administrator. From the main menu, go to Help > License Activation. Go to the Advanced tab, then the Repair tab. For each broken license listed in the License selector box, click the Generate XML Request button. Save each XML file to a convenient location on your computer. Log in to your FlexSim Account. From the top navigation header click the Licenses link, then choose Manual XML in the Licenses submenu. Upload your XML files by dragging them onto the drop zone. Your uploaded XML requests will be processed. Upon completion, you will be prompted to download each XML response. In FlexSim (your instance opened above in step 1 using Run as administrator), you should still be on the same License Activation > Advanced > Repair tab. Process each response by pressing the Process Response button and browsing to an XML response. FlexSim should successfully repair the license. After repairing it should be usable and returnable.

Trusted Storage   FlexSim is licensed using FlexNet's Trusted Storage. Trusted Storage is a secure storage area FlexNet creates on your license server where it keeps encrypted and hashed license information for licensing FlexSim. Before you can activate a FlexSim license to your license server, its Trusted Storage must be configured. This is done by your license server authenticating with FlexSim's main license server.   Below we'll cover configuring Trusted Storage on your license server. If you're here looking for instructions for standalone licensing, check out the article Standalone - Configure Trusted Storage.   I haven't configured Trusted Storage before - why now?   When your license server communicates over the Internet with FlexSim, this initial Trusted Storage configuration happens automatically and invisibly during the course of the license server's first license activation. The first time you activate a FlexSim license to your license server, your license server and FlexSim's main license server authenticate with each other, configuring your local Trusted Storage, and then immediately activating the requested license.   In other words:   Internet-connected activation = automatic and transparent Trusted Storage configuration.   But you're here because your license server can't communicate over the Internet with FlexSim's main license server. Consequently, your Trusted Storage configuration must be completed manually before activating any license.   Create a Trusted Storage config request   On your license server, in your extracted download folder of FlexSim license server materials, navigate into the folder flexsimserveractutil. Right-click flexsimserveractutil.exe and select Run as administrator. In the FlexSim ServerActUtil program, go to Tools > Manual Activation > Generate Request. Enter a valid Activation ID. You can use our special activation ID configure-ts, but any valid activation ID can work. Enter 1 for the Count (seat quantity). Click Browse to select an Output File. Choose a filename for the saved request. We used configure-ts.xml. Press Save. Press Generate. You've just saved a new XML activation request in the location you selected. You can confirm this is a Trusted Storage config request by viewing the saved XML file in a text editor like Notepad. A configuration request will lack the TrustedHostInformation tag. If your configure.xml file contains that tag, that means your Trusted Storage is already configured. In that case, you can move on to the offline license activation steps for your license server. Otherwise, continue configuring your Trusted Storage below.   Submit your Trusted Storage configuration request   Transfer your Trusted Storage config request XML file from your chosen save location to a computer with Internet access. From your Internet-connected computer, open a web browser and login to any FlexSim Account - even a new guest account will work. Click the Licenses link in the header, then choose Manual XML in the Licenses submenu. Upload your XML request file by dragging it onto the drop zone. Your uploaded XML request will be processed. Upon completion, you will be prompted to download the XML response.   Did you get a red error message instead of a green success indicator?     A message "Fulfill count exceeded the available seat count" means that Trusted Storage is already configured on your license server. In that case, move on to the offline license activation steps for your license server. Otherwise, continue below to finish configuring your Trusted Storage.   Process your manual activation responses   Transfer your downloaded XML activation response to your offline license server. In the FlexSim ServerActUtil program, go to Tools > Manual Activation > Process Response. Browse to an XML activation response file. Press Process. FlexSim should give you an indication of successful processing of your config request.   At this point your Trusted Storage should be fully configured. You are ready to activate your licenses.

  When modeling arrivals or failures, it is common to reuse the inter-arrival time distribution as the one used to sample the time to first event. Except for memoryless processes (e.g., negative exponential), this is not statistically correct and introduces a left-bias where early events occur sooner than they should. The user command in the attached library generates a statistically valid time-to-first-event distribution from a definition of inter-arrival times.   Problem Being Addressed Inter-arrival distributions describe time between events, not time to the first event Reusing the same distribution biases early arrivals/failures Bias is most visible in: Short simulation runs Models without warm-up periods Models initialized with work-in-progress What the Command Does The command generates a sample set for time to first event using inter-arrival data provided as: A FlexScript distribution expression (string) An array of inter-arrival samples An existing Empirical Distribution object The process: Generates a timeline of events using inter-arrival samples Selects random observation points along the timeline Measures time to the next event Stores these values in a new Empirical Distribution object Runs the Fit function to suggest a best-fit distribution and parameters Output A new Empirical Distribution representing time to first event A fitted distribution expression (name + parameters) suitable for direct use Option to sample empirically or via the fitted distribution Typical Use Cases Time to first failure fields Arrival processes where warm-up is undesirable Short-term forecasting models Models requiring statistically defensible early-run behavior Why Use This Approach Avoids bias introduced by reusing inter-arrival distributions Produces statistically defensible results Reduces reliance on warm-up periods Especially beneficial when early statistics matter   How to Use the Command Loading the attached user library will auto-install the required user commands. The command createTTFeventDist creates an Empirical Distribution that represents the time to first event, derived from an inter-arrival time definition. Parameters P1 (string) Name of the new Empirical Distribution object to create. P2 (overloaded) Definition of the inter-arrival times. One of: A FlexScript distribution expression (string) An array of inter-arrival samples The name of an existing Empirical Distribution object P3 (optional integer) Number of time-to-first-event samples to generate and store in the new Empirical Distribution. (Default is suitable for most use cases.) P4 (optional integer) Number of inter-arrival samples used to construct the event timeline. (Larger values improve stability at the cost of run time.)   Example: Time to First Failure from a Weibull Inter-Arrival Process Assume failures follow a Weibull inter-arrival distribution, but the model starts at an arbitrary point in time and does not use a warm-up period. Instead of reusing the Weibull distribution directly for the first failure, generate a statistically correct time-to-first-failure distribution.  Open a script window and run this command with the example parameters: createTTFeventDist( "FirstFailureDist", "weibull(0,120, 1.8)", 5000, 100000);   This command: Generates a large inter-arrival timeline from 100000 samples of  the Weibull distribution Samples valid times to the next failure Creates an Empirical Distribution named FirstFailureDist Fits a theoretical distribution and reports suggested parameters (eg.  beta(-0.08, 356.54, 1.20, 4.89)) Using the Result in the Model You can now use the generated distribution in either of the following ways: Use the fitted distribution expression Copy the suggested distribution name and parameters into a Time to First Failure or arrival field. Reference the Empirical Distribution directly Sample from the Empirical object where a time-to-first-event value is required, choosing either: Fitted distribution sampling, or Empirical data sampling Both approaches ensure the first event is statistically consistent with the defined inter-arrival process.

FlexSim 2026 is now available for download.   You can view the Release Notes in the online user manual.   FlexSim 26.0.0 Release Notes   If you have bug reports or other feedback on the software, please create a new post in FlexSim Forums.

Introduction   A new feature-version of FlexSim Simulation Software is released several times per year. In order for client PCs to be able to run a licensed version of the upgraded software, you may need to upgrade the activated license(s) on your license server. Licenses with a current maintenance subscription are eligible to be upgraded to the latest version.   If you don't understand how licensing works for different FlexSim versions, please review our Answers article FlexSim Version Numbering.   Overview   There are 6 main steps to upgrading the licenses hosted on your lmadmin or lmtools license server:   Check if you need to upgrade your license server files Return the licenses you intend to upgrade Upgrade your licenses Activate the upgraded license Reread the license Upgrade client PCs   Several of these steps have their own fully documented procedures. We'll link you to those resources below.   1. Check if you need to upgrade your license server files   If your organization's license server was installed previously and hosting licenses for FlexSim 25.1 or lower, it may need to be upgraded for compatibility with FlexSim 25.2 and higher. Click here to learn more or go directly to the latest license server files.   After you have upgraded your license server files, move on with the rest of the upgrade process, as outlined below.   2. Return the licenses you intend to upgrade   The steps to return a license-server-based license are fully documented. Choose the link below that best matches your needs, depending on whether your license server can connect to the Internet:   License Server - Return - Online License Server - Return - XML / Offline   Be sure to return ALL licenses you wish to upgrade.   3. Upgrade your licenses   NOTE: Licenses with expired maintenance will not upgrade. Timed licenses do not upgrade. Only permanent (not timed) licenses under current maintenance can be upgraded. Contact your salesperson for extending a subscription or other circumstances.   Log in to your FlexSim Account.   If you were already logged in to your FlexSim Account, in the top navigation menu hover over your initials icon and choose Reload Account.     Now in the top navigation menu, choose Licenses > List.     Check that the available seat count is equal to the total. All of a license’s seats should be returned for it to upgrade.   Click on the Upgrade Licenses button.     If you have several licenses to upgrade and all are owned by or shared with your FlexSim Account, they will all be upgraded at once. Please be patient while the upgrade process works in the background.   When the page refreshes, eligible licenses will have a new activation ID for the latest version of the software. Your license code indicates its version at the end of the code to help you know what versions your license will properly activate. Review license code format.   4. Activate the upgraded licenses   The steps to activate a license-server-based license are fully documented. Choose the link below that best matches your needs, depending on whether your license server can connect to the Internet:   License Server - Activation - Online License Server - Activation - XML / Offline   5. Reread the license   Your license server needs to start serving up your newly activated licenses. You can either restart your license manager service, or use your license manager's option to reread your licenses.   The steps to reread your licenses differ depending on which license manager you are using to host your licenses. Use these links to jump to instructions for the license manager you're using:   lmadmin lmtools+lmgrd   6. Upgrade client PCs   Finally, upgrade your PC with a version of FlexSim appropriate for your new license (learn how licenses work across versions).   After installing a new version of FlexSim, you will need to configure it to get a license from your license server. There are two ways a client PC can be configured. Choose the method below that most closely matches the main use case for your client PC:   Single-user client PCs - this method configures settings that are saved on a per-user basis. Multi-user client PCs - usually appropriate for a university computer lab or other shared-PC situation, where the configuration should be computer-based.   Having trouble licensing your client PC?   Verify client PC licensing to find out if your client PC is successfully getting a license from your new license server. Diagnose Client/Server connectivity issues that may be preventing your FlexSim software from obtaining a license. Discover other issues that may be preventing your client PC from obtaining a license by working through our License Server Troubleshooting tips.  

You've installed, configured, and started your license server. FlexSim is installed and your client PCs are set to get a license from your license server. How can you tell if they're communicating and licensing properly?   You can check both the client PC and the license server to make sure that licensing is happening:   Client PC   Within FlexSim software on the client PC, go to the main menu, Help > About FlexSim. The popup should indicate the activated license type. Test licensed features to see if they work. Check the article FlexSim Feature Limitations by License Type to see what features should be available given your license type (Enterprise, Educational, Student, Runtime). For instance, the Experimenter feature should be available to each of those license types.   License Server   In lmtools logs (Config Services > View Log…), you should see that a seat is in use. (See How do I read/analyze my vendor daemon logs? What do the various lines mean?). . In lmadmin logs you should see that a seat is in use.   If your client PC is not getting licensed and/or your license server logs don't indicate communication with a client PC, check the license server troubleshooting steps.  

When installing FlexSim, has the installer ever quit, saying "Installation Cancelled" or "FlexSim must close"?     Installation Canceled Installation was cancelled by user.   Or has your FlexSim installation ever had errors upon starting the software?     FlexSim has encountered a problem. Your work is saved in recovery files. Please notify FlexSim Technical Support. Retrieve your recovery files, then email FlexSim. Do you want to restart?     FlexSim encountered an unrecoverable error and must close. Please notify FlexSim Technical Support about this issue.   This can be frustrating any time, let alone for a brand new FlexSim installation.   Here are some possible solutions that may help FlexSim install or start properly:   1. Meet the System Requirements   Make sure that your computer meets FlexSim's minimum system requirements. If your computer's hardware or operating system is out of spec, you may not be able to install FlexSim, or it may not start or work properly.   Don't overlook the disk space requirement. You'll need about 2.5 GB free for the installer and the completed installation in order to install FlexSim. Low disk space will cause the installation to fail.   Graphics specifications are particularly important, as incompatible/nonexistent graphics hardware or out of date graphics drivers may cause strange graphics behavior or other issues. See this article for more graphics considerations, tips, and guidance for installing or upgrading graphics drivers.   2. Windows Updates, Driver Updates   FlexSim relies on some newer Windows components and libraries provided by Microsoft in patches and updates. Make sure your computer is up to date with all Windows updates.   In addition to Windows updates, be sure to upgrade your system's graphics drivers, as FlexSim relies on fixes and features found in the latest graphics drivers from NVIDIA, Intel, or AMD. It is not enough to just use Windows Update to check for new graphics drivers - you should check the websites for your system manufacturer or graphics vendor specifically for updated graphics drivers. See our graphics article for more detailed information.   3. Reboot your computer   Windows has improved enormously over the years, but even with modern Windows sometimes a good, old-fashioned reboot can do the trick, especially if you have recently installed or uninstalled other software or Windows updates.   4. Run as Administrator   Software Installation: Ensure that you have the proper privileges on your PC to install new software.   Install FlexSim by right-clicking the installer file and choosing Run As Administrator. If you don't have admin rights, you will be prompted to enter credentials with admin rights. Enter the proper credentials to allow the software installation to proceed.     Startup Issues: Try starting FlexSim with higher permissions by right-clicking the program icon and choosing Run As Administrator. If you don't have admin rights, you will be prompted to enter credentials with admin rights. Enter the proper credentials and the software should start with elevated permissions. Does this solve the problem?   Some users have reported that some FlexSim components are blocked by default, but can run properly when FlexSim is started with elevated privileges.   If you find this is the case for you, work with your IT group to determine how to unblock the DLLs or other components required by FlexSim.   5. Delete FlexSim's saved settings   Sometimes when FlexSim has trouble starting up, it can be due to a corrupted prefs.t file. FlexSim's prefs.t file stores your FlexSim settings and preferences and is located at:   %APPDATA%\Flexsim\FlexSim <version>   The %APPDATA% address is a shortcut to your Windows user account's Roaming directory. This animation shows how to get to your %APPDATA% directory:     With FlexSim closed, delete this prefs.t file. Then try starting FlexSim. Are the problems resolved?   6. Reinstall FlexSim   Completely uninstall FlexSim and try a new installation. It may be worth downloading a new copy of the full installer to ensure there was no corruption in the install package.   You could also try the .msi installer, instead of the .exe. When installing using the .msi you can save a log of the install process. This could help with debugging if there are still problems.   Whichever method you use when reinstalling FlexSim, be sure to right-click the installer and choose to Run as Administrator (see the Run as Administrator section above).   7. Update your computer's .NET installation   FlexSim relies on Microsoft's .NET Framework for some functionality. Windows 10 includes a compatible .NET version, or if a compatible version is missing the FlexSim installer will try to download and install .NET directly from Microsoft. If your computer/network does not allow this you may need to update .NET yourself. Click here to download the .NET framework directly from Microsoft.   After installing the .NET Framework, please revisit the Windows Updates section above. Microsoft may provide new security fixes that should be applied to your .NET installation.   8. Reinstall Microsoft Visual C++ Redistributable   These are run-time components provided by Microsoft that are required to run FlexSim. Normally these components are installed during FlexSim's installation process. If FlexSim is encountering errors, it could be caused by a broken or out of date C++ redistributable. Click here to download the latest Visual C++ Redistributable directly from Microsoft.   After reinstalling the Visual C++ Redistributable, please revisit the Windows Updates section above. There may be new security fixes for the redistributable.   9. Antivirus   We have seen instances where FlexSim is blocked by an overzealous Antivirus software. If FlexSim doesn't start up at all, despite a new installation, this could be the case.   To test this, temporarily disable your antivirus and try to install or start FlexSim. If the problem clears up then your antivirus may indeed be blocking FlexSim. In this case, work with your IT department to configure the appropriate settings to allow FlexSim to run alongside your antivirus solution.   Remember to re-enable your antivirus software after this test.   10. Windows Event Viewer   If FlexSim still won't install or start, try checking the Windows Event Viewer to see if there are any errors related to installing or starting FlexSim. If so, please send those our way so that we can troubleshoot further. In case you've never used it before, here is a tutorial covering the Event Viewer.   Add your comments below on what did or didn't work for you, other problems or symptoms you encountered, or tips and tricks that helped you solve them.   Fixes for older versions   The following suggestions apply to outdated versions of FlexSim.   Update OpenSSL DLLs   Applies to FlexSim versions 7.0.0-20.2.0 (excluding LTS versions 20.0.9+) Some older FlexSim installations may crash shortly after FlexSim opens, when FlexSim's start page contacts our remote servers for dynamic content, due to a new system incompatibility with the openssl library that shipped with these older FlexSim versions.   Newer versions of FlexSim include updated files that resolve this problem. Install the latest version of FlexSim to obtain updated versions of the following two files:   C:\Program Files\FlexSim <version>\modules\Emulation\openssl\libeay32.dll C:\Program Files\FlexSim <version>\modules\Emulation\openssl\ssleay32.dll   Copy those updated DLLs to your affected FlexSim installation, under its program\Webkit folder, overwriting the older version of those files.   Alternate workaround: disconnect your computer from the Internet, both wired networks and Wi-Fi. Start FlexSim. Go to File > Global Preferences > Dynamic Content tab. Deactivate all of the options there. You can now reconnect to the Internet and FlexSim may work properly the next time you start the application.   Uninstall KB4571756   Applies to FlexSim versions 7.7.0-16.2.2   A Windows 10 patch released in September 2020 may prevent FlexSim versions 7.7.0-16.2.2 from starting.   If you are using one of these older versions of FlexSim and the program will not start, try removing this Windows update: https://support.microsoft.com/en-us/help/4571756/windows-10-update-kb4571756  

Why would I delete a fulfillment?   You may need to manually delete a fulfillment from your PC if:   Your license is broken. Sometimes you can fix this problem yourself by attempting a repair. However, you may get a message that the repair failed. "Repair: failure. Online return/repair request for the activation ID is not originated from the original client machine." In this case contact your local FlexSim distributor to explain the situation and let them take a look. Reference this post. If they determine it is best to delete the broken fulfillment, follow the instructions below to do so. Your distributor will then force-return the broken license so that it will be available for a new activation. You mistakenly requested a force-return of a license. If you later find the fulfillment that you thought was lost, that fulfillment is no longer able to be returned normally (because it was already force-returned).   In these cases, and in a few other rare circumstances, you may find it necessary to manually remove a fulfillment from your computer. This process occurs exclusively on your computer without any communication with FlexSim's main license server.   Delete your fulfillment   FlexSim 23.0 or greater   For FlexSim version 23.0.1 or greater, you can delete fulfillments using the License Activation window.   From FlexSim's main menu, choose Help > License Activation. Under the Advanced tab, find the Delete sub-tab. Choose the fulfillment you'd like to remove from your computer and click Delete. Confirm your choice to remove the fulfillment from your computer.     Currently licenses that are *BROKEN* do not show up in this list (how do licenses become broken?), so if this applies to your situation you will need to use the Older versions method below.   Older versions   If you are using an older version of FlexSim, we recommend that you download the latest FlexSim software and use the updated delete method described above, even if your license is for an older FlexSim version. Older FlexSim versions do not have a graphical interface for removing fulfillments, but if you're comfortable you can still do so using a FlexScript command.   Find the fulfillment ID   The first step is to find the fulfillment ID of the license you want to return. This is an identifier unique to the activation you're removing.   View your licenses to find the fulfillment ID you wish to remove from your PC.   Prepare your delete command   Once you know your broken fulfillment ID, you're ready to build the command that will remove it from your computer.   licenseactivation(LA_DELETE_FULFILLMENT_RECORD, "paste entire 'FID_...' fulfillmentID here");   Be sure to paste the complete fulfillment ID into the 2nd parameter.   Depending on your software's licensed state, you may be able to run this command directly in a script window. If not, we'll work around that limitation by using an object's reset trigger.   Execute the delete command   There are two ways to manually delete your fulfillment:   Run the command in a script window Use a 3D object's reset trigger   Run in a Script window   If your FlexSim installation is still licensed, you can open a Script window to run FlexScript commands:     Run the command console. You will be prompted to confirm that you truly want to remove the fulfillment:     Choose Yes to remove the fulfillment.   Use a 3D object's reset trigger   If your FlexSim software is not licensed the Script command console is not available. Instead, do the following:   Create a new model. Drag any object into the 3D view. Create a reset trigger on that object. Enter the FlexScript command into the reset trigger. Press OK to save the script. Reset the model. Choose Yes to confirm that you truly want to remove the fulfillment.  

Autodesk has released a module that provides better functionality between FlexSim and Autodesk software. FlexSim users can download the module by navigating to the “3rd Party Modules” tab on the FlexSim downloads page:   Downloads - FlexSim Account       Please note that the module will work with FlexSim version 24.2.2 or later.   The first release of the module includes the following:   Added support for loading ipt, iam, and rvt files. Added a new AutoCAD FlexScript API. Updated dwg importer using the Mesh API.   More information about the module can be found in the user manual here:   User Manual - ADSK Interop   Instructions and examples of how to use the module can be found here:   Autodesk Interop Module Example Models   You can find a demo of the new features (10:10 - 29:55) in the Autodesk University class recording here:   Elevating Factory Design: FlexSim and the Future of Autodesk Fusion Digital Factory   If you need to report a bug, please make a post in the Bug Report space. If you have a new idea for the software, please make a suggestion in the Development space.  

tl;dr   must be stable and persistent, always able to maintain a constant connection with the client software don't use a user's personal computer as a license server use a currently supported Microsoft OS bare-metal hardware, virtual hardware, cloud hosted - all are fine if the hardware meets the OS specifications, it meets the license server specifications configure your network and firewalls to allow the client-server communication   Use an always-on, accessible server (not a user's PC)   Your license server should be on a stable, persistent system that is always on and always accessible via a stable IP address or fully qualified domain name. A user’s personal system is not a good license server, unless they are only serving licenses to themselves, in which case please consider contacting your local FlexSim distributor to exchange for a standalone license.   Operating System   Hosting FlexSim licenses requires a currently supported version of Windows (desktop or server versions are supported). FlexSim and FlexNet do not support Windows operating systems that have reached their end-of-life. See Microsoft guidance on product lifecycle.   You should perform all Microsoft Updates so that your operating system is fully patched prior to installing the license server software.   In the future we hope to allow FlexSim licenses to be hosted on Linux or Mac license servers, in addition to Windows. Work toward multiplatform is ongoing. We do not currently have an estimated timeline.   Server Hardware   If your license server hardware meets the specifications required for the chosen Microsoft OS, it will be adequate to run the license server software. Hosting licenses is generally NOT a demanding workload.   Please do not confuse these minimal license server hardware requirements with the different and more demanding system requirements for running FlexSim Simulation Software.   Cloud Hosting   Your license server could be hosted by a cloud provider or on premises, on a virtual machine, or a bare-metal OS.   Keep in mind that your license server should be a stable, persistent server that client PCs can remain connected to. If your server setup works by creating and destroying new instances of a virtual machine each time you reboot, it is NOT suitable for use as a license server. You will lose your Trusted-Storage-based FlexSim licenses when the virtual machine is terminated.   Networking, firewalls, connectivity   For the client software to remain licensed, it must maintain a constant network connection to your license server. The exact details of such a configuration are up to you.   If you want to limit client-server connections to the local network, allow access to the license server worldwide over a VPN, or make your licenses available over the public Internet, these are all decisions you must make and configure your network and firewalls accordingly such that your FlexSim client PCs can maintain a constant connection to the license server.   Further networking guidance, including information regarding firewalls and port numbers, is found in the individual instructions for lmtools or lmadmin.  

Recommended System Requirements   This article complements FlexSim's System Requirements. We'll go over each of the major components, discuss their importance to a FlexSim model, and make recommendations to help you decide on the right hardware for your situation.   CPU   Single Model Run   A single run of a FlexSim model (ie not an experiment or optimization run) is single threaded, which means it runs on only 1 CPU core. Buying a processor with more cores won't speed up a single simulation run. To complete single model runs more quickly, use instead a processor with a faster single core clock speed (gigahertz, or cycles per second) or better efficiency (instructions per cycle).   In short, for the fastest individual model runs, you want the fastest processor possible, regardless of the number of cores.   Experimenter or Optimizer - Multiple Simultaneous Replications   When you're doing multiple simultaneous model runs using the Experimenter or Optimizer, FlexSim takes advantage of multiple CPU cores to run simulation replications in parallel.   By default, FlexSim spawns as many replications as you have cores; for example, a Quad core processor enables four single-threaded simulation runs to process simultaneously, one on each core, getting you results four times faster than by using a single core processor at the same speed/efficiency.   If necessary, you can manually limit the number of concurrent replications by setting the Max Cores value from FlexSim's Main Menu under Statistics > Experimenter > Advanced tab > Max Cores input field. Each replication consumes some amount of system RAM, so if you run out of RAM before you run out of cores, it may be necessary to limit the number of cores used to run replications.   Conclusion   If you’re primarily doing single simulation runs, choose a faster processor speed regardless of the number of cores. If you’re primarily doing experiments, choose a processor with a high number of processing cores (and make sure your system has enough RAM to support them - see the Memory heading, below). If you’ll be doing both, choose a processor that strikes a good balance between core speed and core count.   Memory   Considerations   Random Access Memory, or RAM, is a PC's fast "working" memory, where it stores the data and programs it is currently running (don't confuse this with your much slower hard drive, where data is stored "at rest"). Most consumer Windows computers top out at 32 or 64 GB of RAM, though Windows is capable of supporting much more when coupled with high-end hardware (see limits per OS here).   Your computer is always doing many other things besides just running FlexSim. Your operating system itself has memory needs for all the processes it is constantly running. You probably have an antivirus solution, maybe a backup software, and often other utilities running invisibly in the background. Then there are all the applications you currently have open - your email, a web browser, music streaming, etc. All of these are consuming RAM.   As you plan your FlexSim hardware, be aware that you should have enough RAM to run all these other applications, plus your FlexSim model, plus have a good amount of extra RAM as a buffer.   FlexSim's Requirements   Many FlexSim models will use less than 4 GB of RAM in a single model run, but it all depends on your simulation and data. Some large and complex models can and do go above 4 GB of RAM utilization (sometimes well above). If FlexSim's RAM utilization starts approaching a high percentage of your total available system RAM, your computer will turn sluggish or totally unresponsive as it runs out of memory and begins paging out to disk for its memory needs (which is orders of magnitude slower than RAM).   A FlexSim system should have 16 GB of RAM as a minimum. For the best experience we recommend 32 GB of RAM or more. Many modern consumer PCs meet this recommendation. See FlexSim's latest minimum and recommended system requirements here.   Experiments and Optimizations   Experiments and optimizations run several replications of your model simultaneously, so make sure you have enough total memory in your system so that each replication can hit its peak memory needs, while still leaving enough memory for the system and other running applications (OS, antivirus, other background processes, etc.).   In addition, the experimenter saves statistics data for each replication by default. Each completed replication will send its statistics collectors' data to the main FlexSim thread, where it will ultimately be stored in the results database file on the hard drive. However, several stages of the transfer process require two copies of the data. In addition, all child processes can transfer data simultaneously. So, if you have a model that generates 100MB of statistics data, and you run an experiment with 8 CPUs, and all 8 CPUs finish a replication at roughly the same time, you'll need at least 1600MB (100 MB x 2 x 8) to transfer the data successfully, on top of all the other RAM utilization.   Example Scenario   I've developed a simulation model and now I'd like to run multiple replications using the Experimenter. Watching my simulation run normally, while monitoring FlexSim's memory usage with Windows Task Manager, I see that over the entire course of its run my simulation peaks at about 2.1 GB of RAM at its highest utilization. My computer system has 16 GB of RAM. When FlexSim is not running at all, the system uses about 20% of its resources for the operating system and other background processes. This leaves about 12.8 GB of RAM free. How many concurrent replications of FlexSim can my PC support? 12.8 GB / 2.1 GB per replication = 6.1 concurrent replications So, I might get by with allowing 6 concurrent replications of FlexSim, but I feel like 5 is a safer bet to give the system a bit of headroom, and because running the experimenter and collecting results data also requires some additional memory overhead. Since my computer has a quad-core processor and uses simultaneous multithreading (SMT) (which allows each core to run two FlexSim replications at once), FlexSim's default would be to run 8 concurrent replications. My calculations showed that 8 concurrent replications would be too many, and will probably bog down my PC, slowing or halting the entire process. I will limit the number of concurrent replications the experimenter will use by setting the Max Cores value to 5. This option is set from FlexSim's Main Menu under Statistics > Experimenter > Advanced tab > Max Cores input field.   Your settings will differ from this example. Check your computer's amount of RAM, the peak memory needs of your simulation models, and your baseline RAM utilization when you're not running any simulations. Factor in a reasonable % as a buffer. Use these values to determine how many concurrent FlexSim replications your computer may support.   When allowing FlexSim to use its default of running the max number of replications your CPU supports, please keep in mind that many multi-core CPUs actually run multiple threads simultaneously per core (simultaneous multithreading - SMT). To fully take advantage of all the simultaneous replications that your PC could run at once, be sure to get enough RAM for all the replications your CPU is capable of. For example, a 4-core CPU with support for SMT could run 8 simulation replications at once. Make sure you have the memory to do so! If not, be sure to use the Max Cores option to limit the number of concurrent replications.   Conclusion   A system meeting FlexSim's minimum RAM requirement will have enough memory for a single model run of most simulation models. If your simulations are large or complex, or if you intend on running experiments or using the optimizer, you should meet the higher recommended spec of 32 GB of RAM or more.   Disk   Space Requirements   The FlexSim installer may be up to 1.2GB in size, depending on the FlexSim version.   After installation, FlexSim's program files use up to 1.2GB of disk space. Your model files, CAD layouts, images, custom 3D shapes, import data, exported reports, and other simulation related assets that you provide will take disk space in addition to the software's installed footprint.   Disk Speed   Most FlexSim models will run from memory, so hard drive speed isn't really an issue. However, if you're reading/writing with files/databases while the model is running, disk speed could make a huge difference; a Solid-State Drive (SSD) is a must in that case. Alternatively, try to do data reading and writing before and after the simulation run, if possible.   FlexSim recommends SSDs in general because they make every interaction with your computer feel faster and more responsive. You won't regret an upgrade from a regular, spinning hard drive to an SSD.   Conclusion   Consider upgrading your hard drive to an SSD if you will be reading or writing to files or databases during a model run, or to generally improve system responsiveness. Graphics   Recommended Graphics   The better/newer/bigger/faster the graphics processor, the better the performance. Integrated graphics, where a smaller GPU is packaged into the CPU, have gotten much better in recent years, but a discrete GPU remains the most powerful graphics solution.   FlexSim works best on Nvidia GeForce RTX GPUs, but Nvidia Quadro and AMD Radeon are also good solutions. Most recent integrated graphics solutions meet FlexSim's minimum graphics requirements, but in general will not perform as well as discrete graphics.   Graphics Driver Updates   It is also important to note that you should keep your graphics drivers updated to the latest version. If your graphics hardware meets FlexSim's minimum requirements but you are experiencing graphical issues in FlexSim, a graphics driver update may solve the problem. Please check out this article for some common symptoms and solutions to graphics issues within FlexSim.   Virtual Reality   FlexSim supports Oculus Rift/Meta Quest 2, HTC Vive, and Windows mixed reality virtual reality platforms (see demo models). Be sure to meet FlexSim's higher recommended specifications if you plan to use VR.   Conclusion   While recent integrated graphics solutions meet FlexSim's minimum requirements, a discrete graphics solution is a better choice. For maximum performance, FlexSim recommends a recent NVIDIA GeForce RTX GPU.  

FlexSim 25.2.0 includes upgraded third-party licensing libraries which require an updated set of license server files based on Flexnet Publisher version 11.19.8.0 or higher. For background, see Version Compatibility Between Components. In terms of that article, the client library linked to the FlexEnabled application (FlexSim) was upgraded, so all the licensing components further up the list also require an upgrade. Thus, FlexSim has a new set of license server files available. Download the new license server files here:   https://flexs.im/lmtools-download   Suggested instructions:   1. Download the new license server files (.zip archive) and extract to a location right next to your previous license server tools, like in this screenshot:     2. Install the latest anchor service: Browse the newly extracted files to find flexsimserveractutil.exe. Right click and choose Run as Administrator. From the main menu of flexsimserveractutil.exe, go to Tools > Licensing Service > Install Anchor Service. This will install the updated version of the licensing anchor service, compatible with FlexSim 25.2 and higher. For more information, see License Server - FlexNet Licensing Service 64.   3. Start the new lmtools.exe from the new folder. Your FlexSim_License service should be listed there.   4. Update the paths for lmgrd.exe, flexsim.lic, and log.log to point to the new files in the newly extracted folder.     5. After editing the three paths, save the service (button in upper right).   6. Check the service using Windows Services. Make sure that the "log on" tab is still set to use a "local system account".   7. Make sure the new lmgrd.exe and new flexsim.exe are allowed through the firewall. See lmtools - Add Windows Firewall exceptions.   8. Restart the service, either from the Start/Stop/Reread tab of lmtools or from Windows Services.   9. After you confirm everything is working properly, you can safely delete your old folder containing the previous version of FlexSim's license server files.   If you run into any troubles, try stopping your existing FlexSim_License service first, then repeat the above steps.  

Not sure about the differences between network and standalone licenses? No worries! Read on for an in-depth explanation of each license model:   Standalone Licensing (Client-Activatable) Network Licensing (Server-Concurrent)   You can also download our printable reference, which includes some example scenarios: Standalone vs Network Licensing.pdf.   Standalone Licensing (Client-Activatable)     Once a standalone license is activated to a PC it remains there permanently until it is returned. The PC could be rebooted, taken offline, or even have FlexSim uninstalled - the license remains on the PC.   The steps to activate and return a license are user-accessible from within FlexSim software. Once FlexSim is installed, there are no special PC permissions required to activate or return licenses.   See our licensing procedures article for instructions for managing your standalone licenses (activate, return, repair, upgrade).   User-managed license movement   The ability for the user to activate and return their license at will is a big advantage. It allows teams the freedom to share a license, while still giving individuals the freedom to take a license off-site or off-Internet. As long as a team sharing a license communicates effectively, the license can be passed around to whoever needs it at the moment, by returning the license from one PC and activating to another.   History Log   FlexSim's main license server logs a license's activation/return history, including who last activated (in case you need to contact someone about returning it!). The license history log can be viewed by any FlexSim account that can view the license. This includes the license owner and any account the owner has shared with.   Your activation IDs (the license codes copied into FlexSim to activate your license) can be shared and visible - including the activation history - with every member of your group. See the Sharing tab on your FlexSim account's Licenses page.   Trusted Storage   Your standalone FlexSim licenses are activated to a special holding area on your computer called Trusted Storage, which exists outside and independently of FlexSim software. FlexSim's activation process will authenticate your computer with our main license server and store your license credentials in Trusted Storage, completely outside of any FlexSim installation.   You could uninstall FlexSim, but your license will still reside in your computer's Trusted Storage. You would need to reinstall FlexSim in order to access the return functionality to move your license off of your computer.   So, you can go ahead and use ANY version of FlexSim to activate ANY version of your license so that it will be stored in your computer's Trusted Storage. Whether the activated license will enable features in your version of the software is a separate question - and as a quick reminder, FlexSim's licenses are backward-compatible, meaning that if you have a 21.2 license, you can use that with any version of the software up to version 21.2.x, including all older versions back to 5.0.   The crux is, your standalone license can be accessed by any version of FlexSim installed on your computer, regardless of what version was used when activating the license, because all versions just put your license into Trusted Storage, and all versions check license rights by reading out of Trusted Storage.   Standalone pros   User-level control of the license gives flexibility in who has the license at any given moment. FlexSim maintains the license server, so you don't have to (avoids complexity of installing, configuring, maintaining, and upgrading your own separate license server). Online tools to see the license history and who currently has the license (via your FlexSim Account). In-software auto-upgrades makes upgrading your license easy.   Standalone cons   People sharing the license need to coordinate who will use it when and remember to return the license when unused. Lost, stolen, or broken licenses require interaction with your local FlexSim rep to fix.     Network Licensing (Server-Concurrent) Let's begin with an overview of the setup (simplified from our license server installation instructions) :   Provision a computer/VM to act as the license server. It should remain powered on and attached to the network at all times. Activate your FlexSim licenses to your local license server. Install and configure the license manager software. Configure firewalls and permissions on the server and/or network to allow communication with FlexSim client PCs.   Next, the client PCs:   Install FlexSim on the client PC. Configure licensing settings in the client software to point to the license server. Configure firewalls and permissions on the client PC and/or network to allow communication with the license server. The network connection between client and server must be maintained throughout use of FlexSim software. If the network connection breaks, FlexSim software reverts to the feature-limited Express mode.   This sort of setup is great for computer labs at universities, for instance, where there are many client PCs, and license server hardware or virtual machine is easy to obtain or already exists. Also, where the client PCs are stationary and always on the network, and where network topology makes it easy for the clients to stay connected to the server.   Opening FlexSim software requests a seat from the organization's license server. Closing the software returns the seat.   Network pros   Allows for management of many licenses (seats) from a single location. Some server settings are customizable (Options files can be quite powerful - see chapter 13). Licenses can never become lost or stranded on client PCs. If a client PC loses its connection to the server, the server will reclaim the seat after a timeout period (default timeout is 15 minutes).   Network cons   Complexity of installing, configuring, maintaining, and upgrading a separate license server. Client PCs must maintain a constant connection to the server. No online record of activations/returns (but you can examine your own raw server logs).  

FlexSim 2026 Beta is now available.   FlexSim 26.0.0 Release Notes   To get the beta, log in to your account at https://account.flexsim.com, then go to the Downloads section, and click on More Versions. It will be at the top of the list.   The More Versions button does not appear when logged in as a guest account. The beta is available only to licensed accounts and accounts that have a license shared with them. Learn more about downloading the best version of FlexSim for your license here. If you have bug reports or other feedback on the software, please create a new post in FlexSim Forums.

Assumed configurations   All steps below assume that you followed the installation instructions as described in our license server installation instructions, and that all FlexSim's license server files were extracted to the location C:\FlexSim_LMTOOLS. Throughout these instructions we will reference files inside that folder.   Reread the license   Within your FlexSim_LMTOOLS folder, right-click lmtools.exe and choose Run as administrator. You may need to accept a permissions prompt. Go to the Start/Stop/Reread tab. Choose the FlexNet License service for your FlexSim licenses. The name of the service could be FlexSim_License, but the service could have been given a different name. Press the ReRead License File button. Close lmtools.