With most applications, the ALTLIB command is in effect from the time that the command is entered until either another ALTLIB command is entered or the TSO/E session is ended.

Examples of applications where the ALTLIB command remains in effect for the duration of the session include TSO/E line mode, TMP READY mode, and TSO/E commands that accept subcommands, such as IPCS. This does not, however, apply to ISPF, ISPF dialogs, and similar programs.