SYSREC data sets
After loading the table space, REORG PLUS deallocates the data set to free the device. The following table lists the circumstances under which REORG PLUS requires an SYSREC data set.
Type of reorganization | SYSREC requirement |
|---|---|
Single-phase table space reorganization when you specify SHRLEVEL REFERENCE or SHRLEVEL CHANGE | Not used References to single-phase reorganizations in this section are for SHRLEVEL NONE only. |
Two-phase table space reorganization | Required REORG PLUS uses this data set to pass information between the UNLOAD and RELOAD phases. |
Single-phase table space reorganization when you specify SHRLEVEL NONE | Optional REORG PLUS writes information to this data set during the REORG phase for restart purposes only. |
For information about performance improvements for this data set, see SYSREC data set.
Methods for allocating SYSREC data sets
You can use one of the methods described in Methods-for-allocating-copy-and-work-data-sets to allocate your SYSREC data sets and determine the appropriate size for the data sets. If you do not use dynamic allocation, you must allocate the SYSREC data sets in your JCL by specifying DD statements.
Number of SYSREC data sets to allocate
Use the information in the following table to determine how many SYSREC data sets to allocate. Partition-by-growth table spaces have special requirements as described after the table.
Reorganization type | Object type | Number of SYSREC data sets |
|---|---|---|
Any | Nonpartitioned table space | One |
Two-phase | Partitioned table space | One or multiple |
Single-phase | Partitioned table space | Multiple or none |
Any | Partition-by-growth table space | See the section that follows |
Partition-by-growth table spaces
For partition-by-growth table spaces, REORG PLUS requires the allocation of additional data sets when you are using partition-level SYSREC data sets and either REORG PLUS can extend the table space or you are performing a full SHRLEVEL CHANGE table space reorganization.
The number of additional data sets is equal to the smaller of the following values:
- MAXPARTITIONS minus the number of partitions in the table space
- MAXNEWPARTS
Although REORG PLUS requires that the additional data sets be allocated, it only uses them if partitions are added to the table space during the reorganization. REORG PLUS deletes unused data sets after the reorganization.
Example
The following example illustrates the additional data set requirements using SYSREC data sets. Assume the following scenario:
- You are performing a partial reorganization of a table space with four partitions.
- The value of MAXPARTITIONS is 6.
- Your SYSIN data set contains the following specifications:
PART 3:LAST
MAXNEWPARTS 3
UNLDDN SYSREC
In this example, REORG PLUS requires four SYSREC data sets:
- One for each of the two partitions that are participating in the reorganization (partitions 3 and LAST)
Two additional for partitions that might be added
That is, MAXPARTITIONS (6) minus total partitions in the table space (4) which equals 2. This value is smaller than the MAXNEWPARTS value (3).
For more information about partition-by-growth table spaces, see Reorganizing-partition-by-growth-table-spaces.
Naming conventions for partition-level SYSREC data sets
JCL rules limit ddnames to eight characters. When you use multiple SYSRECnn data sets, the ddname has two parts: the ddname prefix (minimum of one character) and the nn (one to seven characters). The ddname in the installation options module or on the REORG command becomes the prefix.
The ddname that you specify in the JCL must have the partition number nn appended to this prefix. The nn must match the partition that you are reorganizing, and you must allow sufficient bytes for the partition number to be added to the prefix and still have a valid ddname (eight characters or less).
Dynamically allocating SYSREC data sets
REORG PLUS uses information from the ANALYZE phase to analyze the requirements for the current execution and calculates the optimal file size and number of files to allocate.
Note the following information when dynamically allocating SYSREC data sets:
- When you use dynamic allocation of SYSREC data sets during partition rebalancing, REORG PLUS cannot predict how much data movement will occur between rebalanced partitions. Therefore, REORG PLUS might inadequately size the SYSREC data set for a partition that has a large amount of data rebalanced into it. We recommend that you code the required SYSRECnn DD statements for these partitions in the JCL and specify IFALLOC USE for DDTYPE UNLOAD. Continue to allow REORG PLUS to dynamically allocate all other SYSRECnn data sets. This consideration does not apply when you use the REBALANCE command option to rebalance partitions.
- REORG PLUS deletes the SYSREC data sets when you specify DELETEFILES YES and the reorganization ends successfully.
- If you plan to have REORG PLUS allocate more than 99 SYSREC data sets, use the UNLDDN option to specify a ddname prefix that results in eight characters or less after REORG PLUS appends the highest data set number.
Allocating SYSREC data sets in your JCL
Note the following restrictions when allocating SYSREC data sets in your JCL:
- To enable REORG PLUS to restart any time after the UNLOAD phase for a two-phase reorganization, SYSREC cannot be a temporary data set. For information about how REORG PLUS defines temporary data sets, see Work-file-validity-and-integrity-checks.
- Do not specify FREE=CLOSE for SYSREC data sets.
Do not use SMS extended sequential data sets as SYSREC data sets for multiple reorganizations running in a worklist environment (via the BMC DASD MANAGER PLUS, Change Manager, or Catalog Manager products).
When first using a data set, REORG PLUS defines the data set’s DCB attributes. With an SMS extended sequential data set, REORG PLUS cannot change these attributes. However, reusing the data set, (as with multiple reorganizations in a worklist environment), can require different DCB attribute values, such as different block sizes or record lengths. In this case, REORG PLUS attempts to redefine the attributes but fails.