Auxiliary storage manager (ASM) paging controllers attempt to maximize I/O efficiency by incorporating a set of algorithms to distribute the I/O load as evenly as is practical. In addition, priority is given to keeping the system operable in situations where a shortage of a specific type of page space exists.

If you are using optional storage-class memory (SCM) in addition to the required page data sets, ASM selects the optimal paging medium by comparing the observed latency times for I/O (response times). To ASM, the response time is the average time that it takes to complete an I/O request divided by the number of pages that are serviced by a request. ASM also analyzes data characteristics, critical paging requirements, availability of the DASD (during a HyperSwap® failover, for example) and available storage space before selecting a paging target.

A HyperSwap failover is a data availability mechanism that permits replacing a DASD with a backup DASD. During a HyperSwap failover the DASD is not available for paging, so address spaces in main memory, some of which are critical, cannot be paged out to the disk. In this case, SCM can be used for critical address space paging to reduce the risk of critical data loss.