A Faster DBR but...
by Anita Cheung and Dan Yee, IBM TPF Development
Every customer would like to see the performance of any IBM utility run faster in their production environment. Can the IBM database reorganization (DBR) output phase run faster? The answer is yes with APAR PJ22727 applied to your system. How? This APAR permits you to capture the fixed and pool records to buffered tape devices instead of nonbuffered tape devices. By writing the fixed and pool records to buffered tape devices, the DBR output phase will run significantly faster than when writing to nonbuffered tape devices.
APAR PJ22727 has added a new system generation option whose keyword is DBRBUF. This new option enables DBR to write the fixed and pool records to buffered tape devices. The DBRBUF system generation option is not set by default, so the DBR output phase will capture all record types to nonbuffered tape devices unless its value is changed by the ZSYSG functional message. The ZSYSG functional message enables you to alter the DBRBUF system generation option online. However, the DBRBUF bit is subsystem-shared and can only be changed from the basic subsystem (BSS). Once it is set, it is set for all other subsystems in the TPF system and enables DBR to write all fixed and pool records to buffered tape devices. The new value does not take effect until the next initial program load (IPL) of the TPF system. See TPF Operations for the format of the ZSYSG functional message.
There is a risk in setting the DBRBUF system generation option with the ZSYSG functional message. Data may be lost if there is a system re-IPL or tape error while DBR is in progress. To recapture the data that was lost, you must restart the DBR output phase from the first record type that was written to the tape. We do not encourage you to run DBR on buffered tape devices, but you now have the option of doing so if you find the performance of the DBR output phase inadequate. You may find this new option well worth the risk of a system re-IPL or tape error during a DBR run.