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You should specify a region size for each user and MSO will help you determine when it is necessary to increase a user's storage needs. |
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As a starting point, you should specify a region size of 4 MB per logged in user. You should add 4MB for region overhead, and an additional 4MB if the FastLoad Facility is active. Depending on the FOCUS applications in use, you may need to increase this later.
For example, if you have one service block in the MSO configuration file, with MAXIMUM set to 20 and the FastLoad facility activated, you should specify a region size of (20+2)*4, or REGION=88M.
On some MVS systems, the region size request may be overridden by the IEFUSI exit in MVS. You can determine whether this has happened by examining the message MSO13065, which MSO issues at startup. This message displays the amount of storage actually assigned to the address space. If the system has overridden the requested region size, you will need to change IEFUSI to allow MSO to obtain adequate virtual storage.
You should not specify a region size of less than 16MB, since MVS may interpret this as a request for below-the-line storage instead of above the line. In such a case, the total region size will be a site-dependent default.
MSO issues messages MSO13145 and MSO13144 when a user logon is blocked due to insufficient free storage in the address space. Use these messages to determine when storage needs to be increased. You can increase above-the-line storage by requesting a larger region in the MSO JCL. Increasing below-the-line storage requires either application tuning or splitting the MSO address space into multiple regions.
You can also use the Display Users (DU) display in the MSO Console to monitor actual storage allocations for individual MSO users. With this display, you can project the capacity of the region, assuming the users monitored are representative of your MSO workload.
Keep the following points in mind when viewing the storage allocated to the region, as opposed to individual MSO users, in the MSO Console's DU display:
FOCUS modules are preloaded (based on the NUMBER_READY parameter in the configuration file) and reloaded (after a user logs off, to speed up the next logon). The storage for these modules, and their data areas, is displayed as part of the region's storage until a user logs on.
Some task-level storage cannot be accounted for accurately, and is displayed only as part of the region's storage.
FOCUS and MSO contain many reentrant modules which have their storage allocated to the MSO region. Since the modules are reentrant, their storage doesn't increase as the number of users increases.
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