Assigning priorities for programs with exclusive intent

Application programs that have exclusive use of a segment type are not concurrently scheduled with other application programs that are sensitive to the same segment type. Conflicts in scheduling can occur if the same segment type is declared exclusive by more than one application program.

When a program's PSB includes exclusive use of a segment type, the program is not scheduled concurrently with any other program that is sensitive to the same segment type. Similarly, when a program executes with exclusive use of segment types, other programs that include sensitivity to any of those segments are not scheduled concurrently. Exclusive intent does not use enqueue/dequeue serialization. Programs have exclusive intent declared by PROCOPT=E on a SENSEG or program communication block, or PCB, statement within the PSB generation—if the option K, for key sensitivity, is not appended. Conflicting actions occur only if the same segment type is declared by at least one of two programs intending to reference a segment exclusively.

One case in which programs require exclusive intent occurs when a program that uses HSAM in its PSB is scheduled.

Use care when assigning priorities for programs with exclusive intent. Even if a program is selected for execution, a conflict with its processing intent and that of an already-executing program causes the transaction to drop out of the selection process until the next program termination or region start event.

Exceptions to the use of program isolation are programs that use the PROCOPT=GO option. These programs can retrieve segments that have been altered or modified by programs that are still active. Those changes might be subject to backout. The programs might not update the segments, and there is no enqueue on the segments when the programs retrieve them.