The MAXS parameter in the OAM cataloged procedure specifies the maximum number of Object or Object Backup storage group tasks that can be processed concurrently during an OSMC storage management cycle. If storage management cycles for groups overlap, you can use the MAXS parameter to limit resource consumption. When determining the value for MAXS, take into consideration the number of optical and tape drives that are available for storage management processing to avoid drive contention. If MAXS is not specified, a default of 2 is assigned. (See the discussion of MAXS parameter in 5h Updating the PROCLIB.)

If you plan to use these other types of OSMC functions (such as MOVEVOL, RECOVERY or RECYCLE commands), you need to consider and account for the resources these other types of OSMC functions require first, and then distribute the remaining resources for the OSMC storage management cycle with MAXS.

Optical and tape device availability are the resources most likely to cause contention. Writing active data to optical media during the storage management cycle is done on an Object storage group boundary. No active data is mixed between groups; therefore, each group being processed requires a different optical volume. Concurrent requests for different volumes are likely to result in concurrent requests for optical drives. For example, if you have a single, four-drive library and there are concurrent storage management cycles for four storage groups requiring the writing of data to optical media, all four drives are used. If there are concurrent requests to retrieve data from optical volumes during the cycle, those requests and the processing performed during the storage management cycle contend for resources and detract from the performance of each of the functions. Consider using the MAXS parameter with DRIVE STARTUP THRESHOLD to limit resource consumption for writing objects to optical media during storage management cycles, thereby leaving resources available to mount volumes for retrieval requests.

For object tape volumes, the limits set in the parameters and subparameters of the SETOAM statement for TAPEDRIVESTARTUP, MAXTAPESTORETASKS, and MAXTAPERETRIEVETASKS limit resource contention regarding tape library dataservers. These parameters can work with the MAXS parameter resulting in effective resource utilization of the entire storage management environment. For more information on these and other parameters associated with the SETOAM statement, see SETOAM statements for object tape storage.)

The default value for MAXS is two. This default was chosen as a reasonable value when the configuration includes one library with four optical drives and two stand-alone drives. This default allows for concurrent storage management processing for two storage groups and it also allows for overlapping the writing of backup copies to stand-alone drives with the writing of primary optical copies to the library drives. Also, it leaves spare library drives available for retrieve requests and as alternate drives in case of a drive failure.

MAXS could possibly be increased to four when a second library is added to the configuration. Do not set MAXS to a value larger than the number of optical or tape drives that are available for storage management processing. Before increasing the value of MAXS, you should verify that there is sufficient processing capacity available to manage the increased work load, because processing requirements are heavier for small objects than for large ones. Also, you need to consider the tuning guidance described in Tuning OAM.

In addition, it is necessary to assign Object and Object Backup storage groups across the libraries in such a way that the library work loads are balanced. This storage assignment prevents any library from becoming a bottleneck.