General Information

The GAMS system and all connected solvers can be downloaded from the GAMS website at The use of the software is governed by the GAMS End User License Agreement, which is available on our website and can also be found in the GAMS System directory (eula.pdf). Without a valid GAMS license the system will operate as a free demo system and these size-limitations will apply:

  • Model limits:
    • Number of constraints and variables: 300
    • Number of nonzero elements: 2000 (of which 1000 nonlinear)
    • Number of discrete variables: 50 (including semi continuous, semi integer and member of SOS-Sets)
  • Additional Global solver limits: Number of constraints and variables: 10

The GAMS log will indicate that your GAMS system is running in demo mode:

GAMS 24.8.5   Copyright (C) 1987-2017 GAMS Development. All rights reserved
Licensee: GAMS Development Corporation, Washington, DC   G871201/0000CA-ANY
Free Demo,  202-342-0180,,   DC0000

GAMS will terminate with an error message, if it hits one of the limits above:

*** Status: Terminated due to a licensing error 
*** Inspect listing file for more information

GAMS Licenses

The use of GAMS beyond the limits of the free demo system requires the presence of a valid GAMS license file (gamslice.txt). An appropriate license is required for the GAMS Base Module and for most of the GAMS/Solvers and the GAMS/Solver-Links:

  • The GAMS Base Module includes the GAMS Language Compiler, GAMS-APIs, many utilities, some solvers without size restrictions, and most solvers in "demo" mode with a model size limitation. See details below.
  • A GAMS/Solver connects the GAMS Base module to a particular solver and includes a license for this solver to be used through GAMS. It is not necessary to install additional software. A GAMS/Solver-Link connects the GAMS Base Module to a particular solver, but does not include a license for the solver. It may be necessary to install additional software before the solver can be used.

We distinguish between academic and commercial licenses. Academic licenses can only be used for teaching and research at degree granting institutions Other than evaluation and course licenses, GAMS licenses are perpetual. The first year of maintenance, support and updates is included in the initial purchase of the software. Maintained licenses qualify for free updates, adding components, platform-switching without additional charge, and multi-copy discounts on the same platform. After the first year maintenance can be extended by paying a fee. Licenses are typically limited to a single computer platform type (e.g. Windows or Linux), but there are also licenses available, which will work on any platform supported by GAMS. Free academic licenses are available for certain solvers, for details please follow this link. Please visit the GAMS website for further information about the pricing of an appropriate license.

Installing or updating a license file

A GAMS license file is an ASCII file of six lines, which was sent to you via e-mail. Please copy all six lines into a file gamslice.txt. To use the license please follow these steps:

  • MS Windows:
    • During the setup of the GAMS system you will be asked for the license file. Follow these instructions or watch this video.
    • If you have already installed the GAMS system without a license file or want to replace an existing license file with a new one, copy the file as gamslice.txt into your GAMS System Directory. Alternatively follow these steps: Copy the contents of the license file to your clipboard. Then open the GAMSIDE and navigate to: Help → About. The GAMSIDE will recognize the presence of the license in your clipboard and ask, whether you want to create a license. Note: An existing license file will be overwritten.
  • Linux / Mac OS X: Please copy the file as gamslice.txt into your GAMS System Directory (e.g. /usr/bin/gams).

Below are the references to the detailed installation notes:

Before installing a new GAMS version, please check whether it will work with your current GAMS license. The utility CHK4UPD can be used to see if a newer GAMS version is available and what the newest version is that can be used with a given license. This is done by running CHK4UPD without arguments or by giving the name of a local license file. CHK4UPD is also available through the GAMS IDE and can be accessed through: Help –> Check for GAMS Updates. Below is a sample output for a license, which is still under maintenance:

*** Processing GAMS system directory C:\gams\win64\24.8
*** Reading license file C:\gams\win64\24.8\gamslice.txt
*** Your system is up to date

If your license is no longer under maintenance, you will receive a message like the one below:

*** Processing GAMS system directory C:\GAMS\win64\23.9
*** Reading license file C:\GAMS\win64\23.9\gamslice.txt
*** Your license is 1276 days too old to run with the most recent system
*** The version of your GAMS system is 23.9.5
*** The last GAMS version you can use is 24.1.3
*** Please visit
*** For ordering an update to use the most recent version (24.8.5)
*** please contact your distributor

License Problems

Errors or warnings triggered by a problem with the GAMS license file (license.txt) are reported both in the log file and in the lst file. Below are some typical error and warning messages and instructions how to overcome them.

No License File present

Without a license file GAMS will work as a free demonstration mode with the size limitations stated above. If you have received a license file (gamslice.txt), follow the instruction from the previous section. Do not try to rename it or to modify the contents of the license file.

License File Invalid or Corrupted

Running GAMS with an invalid license will give you an error message like the one below:

*** License File validation failed
*** System downgraded to demonstration mode

Do not try to modify your license file, any change will break it. If the original license file is no longer available, please contact and ask for a copy of your license file. Please attach the license file you are currently using. This error also pops up, if you are using a license file, which was issued for a different platform.

License File expired

If are trying to run an old license file with a newer GAMS distribution, you may get an error message stating:

*** License file too old for this version of GAMS.
*** Maintenance expired 2840 days ago.
*** More than 60 days since expiration, sorry...
*** System downgraded to demonstration mode
*** Run an older GAMS system or renew the license

Replace that GAMS system with the one you got together with your license file (use the CHK4UPD utility mentioned above to find out the latest version you can use with the current license; old systems are available at the GAMS website) or update your license to the current version.

No License (for a particular Solver) found

If one of the solvers you are trying to use is not included in your license file and the size of the model exceed the limits of the free demo version, you will get an error stating:

*** No license found
*** To update your license, please contact your distributor.
*** Too many equations for demo mode

Check whether the default solvers for a particular problem class are included in the license. Please note that some of the solvers call other solvers as a sub-solver, e.g.:

  • GAMS/DICOPT requires an NLP and a MIP solver
  • GAMS/SBB requires an NLP solver
  • MPSGE: If GAMS/PATH is not included in your license, please select GAMS/MILES, which is included in the base system as the default solver for MCP problems.


License file too old for this version of GAMS

The complete message is:

*** License file too old for this version of GAMS.
*** Maintenance expired xx days ago.

If GAMS continues working, you can ignore this warning. However, any forthcoming GAMS distribution will most likely not work, but downgrade to the limits of the free demo system.

License File has expired xx days ago

This warning (without further error messages) indicates that the time limited license (e.g. an evaluation license) will stop working soon and the system will continue with the limits of the free demo version.

The GAMS/BASE Module

The GAMS/BASE module includes: