How to change structure sizes

You can change the size of individual structures by changing the CFRM policy.

Then you should rebuild the structures by using the z/OS® command SETXCF START,REBUILD,STRNAME=strname. Be aware that:

The coupling facility size does not increase unless at least one Db2 subsystem is active when this command is issued.
This command does not work on structures that are actively being duplexed.

z/OS attempts to reallocate a new instance of the structure in the same coupling facility if that coupling facility has enough storage space. If there is not enough space, z/OS looks at the preference list and uses the specified alternate coupling facility. After the space is allocated, Db2 rebuilds the information into the new structure. Any transactions that need the structure must wait until the rebuild is complete. It is best to plan a rebuild when other activity in the system is low.