Assignment of storage frames

Storage containing fixed pages cannot be reconfigured. The operating system assigns storage frames as follows:

However, if a long-term page fix for a non-swappable job requires storage but the preferred storage units are full, the operating system may convert some non-preferred storage to preferred storage. If so, the amount of storage available for reconfiguration will be less than that specified in the RSU parameter. The operating system issues message IAR005I to notify the operator.

If the operator then tries to configure storage offline in preparation for partitioning, the system tries to free enough central storage to support the request. Central storage and the address ranges assigned to that storage cannot be configured offline either logically or physically until the required amount of storage is available.

The operating system normally tries to assign requests for long-term fixed pages to preferred storage frames when the requesting job was initiated as non-swappable. However, an authorized job can be initiated as swappable and, while running, issue a SYSEVENT macro to make itself non-swappable for a short period of time. The job may request long-term fixed pages that are assigned to non-preferred storage. Usually this request is not a problem because the job shortly makes itself swappable again. The system can free the storage that backs the long-term fixed pages when the job is swapped out when the storage is required for storage reconfiguration.

However, a long-running job may make itself non-swappable for long times and also request short-term fixed pages that cannot be freed until the job ends normally. Some of these requests may be satisfied from non-preferred storage. Because the frames cannot be freed by paging them out or by swapping out the job, storage reconfiguration may not be possible.

To resolve this problem, specify such jobs in the program properties table (PPT) in the SCHEDxx parmlib member.