Combining data set extents

You can use the CONSOLIDATE command to consolidate the multi-extent data sets that reside on a single volume and are not excluded from data movement. For eligible data sets that consist of contiguous extents in sequential order, DFSMSdss consolidates data sets without extent relocation. Otherwise, DFSMSdss relocates eligible data set extents if contiguous free space exists on the volume to hold the extents.

The CONSOLIDATE command attempts to consolidate data set extents within a managed space of a volume and perform extent reduction for data sets that occupy multiple extents. When you process a volume with the CONSOLIDATE command, DFSMSdss searches each moveable data set. A data set that either is included or is not excluded from data movement is eligible for extent consolidation and extent reduction. For eligible data sets that consist of contiguous extents that are in sequential order, DFSMSdss consolidates without extent relocation. Otherwise, eligible data set extents are relocated if enough free space exists on the volume to combine two or more. When DFSMSdss has completed consolidation for all eligible data sets, or has executed the amount of time specified in the MAXTIME option, processing is quiesced.

For information about specifying the CONSOLIDATE command, refer toz/OS DFSMSdfp Storage Administration.

Note:

The process of combining data set extents can cause the free space to be more fragmented than it was before the operation began.
Data set extents are not moved between track-managed space and cylinder-managed space of an extended address volume during CONSOLIDATE processing.
Despite the fact that DFSMSdss might perform freespace defragmentation following the consolidation of data set extents, the fragmentation index might be higher following a CONSOLIDATE operation than before the operation began.

As an alternative to CONSOLIDATE, you can use the DUMP command with the DELETE and PURGE keywords to scratch and uncatalog the data sets from DASD after they are dumped. If you restore these data sets to the same DASD, allocation attempts to obtain the space for the entire data set. In general, if the DASD volume has sufficient contiguous unused space, DFSMSdss allocates space in one contiguous extent. If you do not specify ALLDATA and ALLEXCP for sequential and partitioned data sets, only used spaces are allocated.

Attention: Do not use this technique for unmovable data sets such as ABSTR allocated or indexed sequential data sets. DFSMSdss does not delete unmovable data sets and the volume might become more fragmented after combining data sets extents than it was before the operation began. If that happens, you might not be able to restore the data sets.

Use the following steps to dump and delete (scratch and uncatalog) all movable non-VSAM data sets, defragment volumes, and restore all movable non-VSAM data sets.

Enter these control statements to dump and delete all movable, single-volume, non-VSAM data sets:

 DUMP INDD(DASD1) OUTDD(TAPE1) OPTIMIZE(3) -
   DATASET(BY((DSORG,NE,VSAM),(ALLOC,EQ,MOV),(MULTI,EQ,NO))) -
   DELETE PURGE

Enter this control statement to defragment the volume:
```
DEFRAG DDN(DASD1)
```
Enter these control statements to restore and catalog all dumped data sets:
```
RESTORE INDD(TAPE1)  OUTDD(DASD1) -
   DATASET(INCLUDE(**)) -
   CATALOG
```

Enter this control statement to defragment the volume, and perform extent reduction if possible:

DEFRAG DDN(DASD1) CONSOLIDATE DDN(DASD1)