Deallocating structures by force

In a few exceptional cases, you might need to deallocate a structure by force to get Db2 restarted.

When you forcibly deallocate an SCA or lock structure, it causes a group restart on the next startup of Db2. Db2 can then reconstruct the SCA or lock structure from the logs during group restart.

To deallocate structures, use z/OS® SETXCF FORCE commands to delete persistent structures or connections. Each Db2 structure requires a different set of commands.

For the group buffer pools:

SETXCF FORCE,CONNECTION,STRNAME=strname,CONNAME=ALL

For the SCA:
```
SETXCF FORCE,STRUCTURE,STRNAME=strname
```

For the lock structure:

SETXCF FORCE,CONNECTION,STRNAME=strname,CONNAME=ALL
 
SETXCF FORCE,STRUCTURE,STRNAME=strname

Important: If your site is running z/OS with APAR OA02620 applied, you cannot delete failed-persistent connections to the lock structure unless you also deallocate the lock structure. Deleting failed-persistent connections without also deallocating the associated structure can result in a loss of coupling facility data. This situation can then cause undetectable losses of data integrity. APAR OA02620 protects your site from data corruption problems that can occur as a result of deleting retained locks. In doing so, the APAR also prevents extended outages that would result from long data recovery operations.

APAR OA02620 makes deleting persistent connections and structures easier. When you forcibly deallocate the lock structure, the operating system deletes failed-persistent connections to the structure for you. Instead of issuing the SETXCF FORCE command twice (once for failed-persistent connections to the lock structure and once for the lock structure itself), you need issue it only one time:

SETXCF FORCE,STRUCTURE,STRNAME=strname