Extra query block


Extra query block support on servers with DB2® Universal Database (UDB) for OS/390® and z/OS® Version 7 or later is configured via the EXTRA BLOCKS SRV parameter on the DB2 DDF installation panel. This support is configured by way of controlling the maximum number of extra query blocks that DB2 can send back to a client for a request. You can set this parameter to a value between 0 and 100. Setting the parameter value to 0 disables the return of extra query blocks. The default value of 100 should always be used to get the most benefit out of this feature, barring any idiosyncrasies in the network that would render this setting less than ideal.

On the client side, where the application accesses DB2 for z/OS either directly through a co-located DB2 Connect™ installation, or through a separate DB2 Connect server installation, there are various means for activating the corresponding DB2 Connect support on a per cursor or statement basis:

DB2 Connect can enable extra query block support using different SQL APIs:

Embedded SQL



The user can invoke extra query block support for a query through the setMaxRows method. Similar to the CLI/ODBC enablement, DB2 Connect will tag on the 'OPTIMIZE for N ROWS' clause for a DB2 for OS/390 and z/OS 6.x server. DB2 Connect will also tag the 'FETCH FIRST N ROWS ONLY' clause for a DB2 for z/OS 7.1 or above server.

Parent topic: DB2 Connect tuning