Formatting newly initialized (reinitialized) volumes for an OLDS
Before using a newly initialized or reinitialized volume for an online log data set (OLDS), you must format the volume or space occupied by the OLDS. There are several techniques for formatting the volume or space.
Attention: If a newly initialized (or reinitialized)
volume is to contain an OLDS, before it can be used in the online
production system, you must format the volume or space occupied by
the OLDS. If it is not formatted, or if the block size of the new
OLDS is not the same as the existing OLDSs, severe performance degradation
and excessive device and channel utilization can be expected until
the OLDS is filled once. This problem is noticeable during emergency
restart and XRF tracking/takeover.
When formatting the volume or space, the blocks must have the same size as that specified in your OLDS definition. Each block must start with a halfword that is filled with the block size (in hexadecimal), and the remainder of each block must be filled with binary zeros.
Although IMS does not provide a formatting utility, many techniques for formatting are available, such as:
- Copy an existing OLDS (of the same size) into the new OLDS.
- Copy an existing volume into the new volume, rename the OLDS to a new name, and delete unrelated VTOC entries.
- Use another IMS subsystem to fill the OLDS (turn on all traces to the log, and issue checkpoint commands until the OLDS is filled).
- Write your own program to write at least 1 byte of data in each track on the volume, or to fill the OLDS with the maximum number of LRECL blocks.
- Use the z/OS® IEBDG utility to format the OLDS.