When you activate the IPCS dialog for a logical screen, the IPCS dialog establishes an ALTLIB environment with the same search order that is in effect before the first ALTLIB command is invoked. See Search order for libraries for the order in which TSO/E searches the libraries. This environment is used solely for IPCS dialog processing for the logical screen.

Although the initial environments are similar, the IPCS environment maintains a separate ALTLIB environment from that of ISPF. IPCS controls separate ALTLIB environments for each ISPF logical screen in which the IPCS is invoked.

When you direct commands to the IPCS dialog, the EXEC command uses the ALTLIB environment associated with the ISPF logical screen in which the IPCS dialog is invoked. When you direct the ALTLIB command to the IPCS dialog, defining or excluding one or more libraries, only the ALTLIB environment associated with that IPCS dialog for that logical screen will change.

When you direct commands to ISPF within the IPCS dialog, the EXEC command uses the ALTLIB environment associated with the particular ISPF application that IPCS is running. When you direct the ALTLIB command to ISPF, only the ALTLIB environment associated with that ISPF application will change.

Only the IPCS dialog maintains a separate ALTLIB environment. Native IPCS does not maintain a separate ALTLIB environment.

For more information about using the ALTLIB command when the IPCS dialog is active, see z/OS MVS IPCS User's Guide, and z/OS MVS IPCS Commands.