Diagnosing Storage Problems
Storage problems typically manifest themselves via the MSO13144/MSO13145 messages or by producing storage-related system abends. The following points should be considered in diagnosing storage problems:
- Is the address space large enough? In MSO Capacity Planning and Performance the requirements of virtual storage for MSO are discussed. As a starting point, you might want to allocate all available below-the-line storage and 4 megabytes per user above the 16MB line.
- Is MVS allocating the requested storage? Some sites restrict virtual storage through the IEFUSI exit in MVS. The MSO13142 message, issued at MSO startup, will confirm the amount of storage available to MSO.
- Are appropriate values specified for STORAGEABOVE and STORAGEBELOW in the MSO configuration file? In general, you should not use numbers that are lower than the defaults, but might need to increase the values, depending on application storage requirements.
- Are applications using an unusual amount of storage? If so, you should allocate a larger address space, and should increase STORAGEABOVE and STORAGEBELOW appropriately. You can use the Display Users panel in the MSO Console to determine actual storage utilization by an application.
- How long has the MSO address space been active? Eventually, due to storage fragmentation, even the largest address space will run out of large contiguous areas of storage. If MSO has been active for more than a few days, it is possible that fragmentation has occurred. In this case, the only solution is to recycle the MSO address space. You should schedule regular, possibly even daily, recycling of MSO in order to prevent this situation.