It is important to watch out for signs that the pool structure is becoming full, as this might have a serious impact on all the applications that are using the pool.
Use the DISPLAY POOLSTAT server command to display the current usage level of the pool structure. The DISPLAY POOLSTAT command produces messages DFHXQ0432I, DFHF0432I or DFHNC0432I. The most important information in these messages is the maximum percentage of lists, entries, and elements, used during the current statistics interval. For the named counter server, message DFHNC0432I only shows the number of entries because there is always one list and no elements.
Messages to the operator, for example DFHXQ0411I and DFHXQ0412I, are issued when threshold levels are reached for the numbers of entries or elements used. Further messages are issued if the pool becomes full. You can set up automated operations processes to watch for these messages and alert your operators to the situation, or take corrective action, if necessary.
You can use the MVS™ operator command SETXCF ALTER,START with an increased SIZE option, to expand the structure, if the structure has not yet reached the maximum size that is defined in the CFRM policy.
The coupling facility resource management (CFRM) policy can specify the keyword ALLOWAUTOALT(YES). This allows the operating system to issue an ALTER command automatically when the structure is near to becoming full, to increase its size or to adjust the ratio of elements to entries. The threshold at which this happens is specified by the FULLTHRESHOLD keyword in the policy. The default threshold is 80%, which is the same as the default threshold at which the server itself issues an automatic ALTER command to optimize the ratio of entries to elements. The server's automatic ALTER process is more sophisticated, because it takes into account the peak usage of the structure within the current statistics interval, rather than just the current usage. Therefore it is best to ensure that the server's automatic ALTER process is triggered first, by making sure that the percentage values of the server's ENTRYWARN and ELEMENTWARN parameters are at least 5 percent less than the percentage value of the CFRM FULLTHRESHOLD keyword.
If the structure has not many entries or elements left, but it has already reached its maximum size, you can still use system-managed rebuild to expand it dynamically without closing down the servers, if all the systems using the structure are at a level which supports this function. First update the CFRM policy to increase the size to the required value, and then activate the updated policy using SETXCF START,POLICY. After this, you can rebuild the structure. The rebuild allocates a new instance of the structure that uses the updated policy, copies across the existing data, and then discards the old instance.
If the number of data lists specified via the MAXQUEUES or MAXTABLES server parameter is too small, an attempt to allocate a new data list will fail with message DFHXQ0443 or message DFHCF0443. There is no way to increase the number of lists without deleting and recreating the structure, which necessitates closing down all of the servers temporarily. You cannot use system-managed rebuild to increase the number of data lists because it copies this number from the existing structure.
You can preserve existing data by using the server program to unload it to a sequential file, and then using SETXCF FORCE to delete the existing structure. You can then use the server program again to reload the data, and allocate a new structure with the appropriate MAXQUEUES or MAXTABLES parameter.
If the pool structure is no longer required, or all of the data in the structure is to be discarded, you can delete a pool by closing down all the servers for that pool, and then using the SETXCF FORCE command to delete the structure. If the server is subsequently started again for the same structure name, an empty structure will be created using the information in the active CFRM policy and the server initialization parameters.