Performance considerations

Buffer usage

The offline reorganization function automatically determines the number of buffers that will be required before reorganization.

This automatic determination of buffer requirements is an advantage over other reorganization utilities. Other utilities require the user to estimate the number of buffers that are required before reorganization and will fail if the estimate is insufficient.

Area analyses during reorganization

If you have a license for the Fast Path Analyzer/EP product, quick (checksum) pointer validation will be performed by default during the reorganization function. The I/O that is required to read the UOW and IOVF control intervals is shared between the two functions.

Because the reorganization process does not access SDEP control intervals, additional I/O is required to read these control intervals if you request SDEP pointer validation. This I/O, however, can be shared with the image copy function.

For more information, see DEDB analyses during reorganization. For example, you can control the level of pointer validation or turn pointer validation off, depending on your performance considerations.

Output image copy during reorganization

If you create one or more output image copies while performing a reorganization, the I/O that is required to read the UOW control intervals is shared between the two functions. Unlike the reorganization process, the image copy process requires IOVF control intervals to be processed sequentially. Consequently, the I/O that is required to read the IOVF control intervals for the image copy is not shared. The I/O that is required for processing of the SDEP control intervals is shared between image copy and analysis functions.

When the process is completed, the reorganization function notifies DBRC that an image copy is required for each area by setting the 'Image Copy Needed' flag. You can use the IC subcommand to request that an image copy be created for each area during the reorganization. DBRC is informed (NOTIFY.IC) when this image copy is created successfully, which resets the 'Image Copy Needed' flag.

If you do not take an image copy during the reorganization process, a message is issued to indicate that an image copy must be taken before each area can be updated online.

Message suppression

For each anomaly that is encountered in an area, the reorganization function generates a message with a specific suffix (severity) level.

When the number of places that a particular condition exists is large, a large number of messages is produced. You can reduce the number of repetitious messages produced by using the MESSAGE_SUPPRESSION keyword to specify the maximum number of times that an informational, warning, error or critical message is to be produced. For the reorganization process, this keyword functions in the same manner as it does for the Fast Path/EP analysis process.