Dynamically Increase MIM List Structure Size
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Dynamically Increase MIM List Structure Size


Article ID: 243722


Updated On:


MIM Resource Sharing (MIM)


Occasionally, customers utilize the MIM DISPLAY CFSIZE to ensure their control file sizes are within acceptable capacity; for those who need to increase their list structure sizes, MIM provides an instruction set to make this change dynamically.


Release : 12.5

Component : MIA, MIC, MII, MIM


To perform this scenario, first issue the MIM DISPLAY CFSIZE command:

Control file size required for current ENQ workload: 27274 Kb               
Control File Size required for peak    ENQ workload: 31561 Kb               
E File Cur Size Rec Sz(Kb) Name                                             
- ---- -------- ---------- --------------------------------------------     
*   00    25000      42435 MIMI#TABLE00                                     
    01    30000      42435 MIMI#TABLE01      

In the above case, it's recommended the site increases their control file list structures using the method detailed below.


  1. Define new primary and secondary list structures and do any CRFM policy steps. The size of the new structures vary based on site but it's generally, the sizing schema is:
    1. make the primary 10-15% larger than recommended size
    2. make the secondary 25-30% larger than the primary structure

  2. Issue the MIM ALLOCATE command to define both new primary and secondary structures to MIM

  3. Issue the MIM DISPLAY FILES command to identify the IDs of the new list structure datasets

  4. Using the MIM MIGRATE command command, migrate off the in-use list structure to the newly allocated primary structure. Re-issue DISPLAY MIM FILES to ensure the new structure is marked "IN-USE".

  5. To remove the old list structures, issue MIM DEALLOCATE commands for both the former primary and secondary list structures

  6. Update the MIMINIT parmlib member with the new list structure datasets

  7. Set another CRFM policy to remove the old MIM list structures. This can be performed any time now that the files are deallocated from MIM usage.

Additional Information

While MIM provides full support for system-managed rebuild of coupling facility structure control files, the MIM Programming Guide does state:

"[that] the MVS REBUILD command [cannot be used] to change the size of a MIM list structure. Instead, use the MIM DEALLOCATE and ALLOCATE commands".