The TSOLIB command provides system and application programmers with a means of linking to different versions of load module libraries while remaining in their active TSO/E session. TSO/E searches these libraries before those specified in the user's logon procedures and those searched by default. This provides for reduced access time to the modules the programmer may be working on and allows a flexible way to change a user's environment.

With the TSOLIB command, a previous habit of having different user IDs or different logon procedures available for these users is no longer required.