DSNB325A csect-name THERE IS A CRITICAL SHORTAGE OF SPACE IN GROUP BUFFER POOL gbp-name
Explanation
The amount of storage in the group buffer pool (GBP) coupling facility structure available for writing new pages is critically low. The primary or secondary GBP is 90 percent full with changed data. (A gbp-name that ends in SEC is a secondary GBP in a duplexing environment.)
As the GBP fills with changed data, the castout thresholds are continuously reached, and the castout engines must continuously work to attempt to keep the number of changed pages in the GBP below the castout thresholds. In addition, the more the GBP is filled with changed data, the less efficient are the coupling facility storage management algorithms. Completely running out of GBP storage can result in transaction delays and in pages being added to the logical page list (LPL).
System action
DB2® processing continues.
This message is non-scrollable. It remains highlighted on the console until you take the appropriate action.
This message might not be automatically deleted in a pre-SP5.2.1-JES3 environment.
Operator response
Contact the system programmer to fix the storage problem.
System programmer response
- Use the ALTER GROUPBUFFERPOOL command to lower the CLASST and GBPOOLT castout thresholds.
- Use the ALTER GROUPBUFFERPOOL command to lower the GBPCHKPT GBP checkpoint frequency.
- Use the MVS™ SETXCF START,REBUILD command to expand the GBP coupling facility structure. If you rebuild, you can use the ALTER GROUPBUFFERPOOL command to lower the RATIO so that a higher percentage of the GBP storage is given to data entries over directory entries.
- If you are running on MVS 5.2 or a subsequent release, you can use the MVS SETXCF START,ALTER command to expand the size of the GBP (the maximum size to which you can expand is determined by the SIZE parameter in the CFRM policy that was used to allocate the GBP).
If you do not do anything to relieve the storage shortage, message DSNB228I appears if a write to the GBP fails due to a 'GBP full' condition. If DB2 detects a 'full' condition, it will suspend the transaction, initiate castout activity, and then retry the write to the GBP. If the GBP write still fails after several retry attempts, then DB2 adds the page to LPL.
Message DSNB327I is displayed when the GBP storage shortage is relieved.
You can monitor the amount of GBP storage in use with the DISPLAY GBPOOL command and with the DB2 statistics trace. Monitor the castout activity to ensure that castouts are keeping up with the rate of GBP-write activity. You can use Performance trace classes 20 and 21 (specifically, IFCIDs 0261, 0262 and 0263) to do more detailed monitoring of the DB2 castout processing.
