When a failure occurs that involves an application program that has enabled persistence, VTAM® closes the ACB on behalf of the application program but retains the LU-LU sessions. The application program enters the recovery pending state until a recovering application issues OPEN ACB. VTAM changes the primary logical unit (PLU) state and secondary logical unit (SLU) state to inhibited. The PLU and SLU states determine whether the application program can accept new sessions. (See Table 1 for more information.) All resources that will be needed if the sessions are restored remain allocated to that application program.

If an application program has enabled persistence and an operator issues a VARY INACT, ID=appl_name, TYPE=FORCE command for that application, VTAM overrides persistence and terminates the application and its sessions normally. With SNPS persistence is also overridden by a HALT command.

If the application has set a persistent session timer (PSTIMER) on the SETLOGON macroinstruction, VTAM ensures that recovery occurs within the specified time limit. The timer is started by application failure and continues until either the time limit expires or the recovering application issues the OPEN ACB. If the timer expires, VTAM terminates the retained sessions as if persistence had not been enabled and releases the held resources. If PSTIMER is not set, the application remains in pending recovery state until the application reopens its ACB. See SETLOGON—Modify an application program's capability to establish sessions for more information about application programs' session-establishment capability.