OLREORG (Reorganize a Database Online) › Using Empty Blocks in OLREORG

Using Empty Blocks in OLREORG

When the amount of free space is limited in used data blocks, the DBUTLTY function OLREORG allows the use of empty blocks in a reorganization.

Support for the OLREORG empty block feature includes the following categories:

• Implementation of a way to keep track of empty blocks
• New DBUTLTY behaviors
• Changes to the REPORT produced by OLREORG
• External limits

Keeping Track of Empty Blocks

CA Datacom/DB keeps track of the available space of a data area using a special key ID in each DBID index. Data space option 1, basic space reclamation, and 2, wraparound mode, do not keep track of which blocks are logically empty, that is, blocks that were used in the past but currently have all their rows deleted.

To enhance the efficiency of OLREORG, the following space options were added that keep track of empty blocks:

• Option 4 is basic space reclamation with an empty block index.
• Option 5 is wraparound mode with an empty block index.

If you plan to use OLREORG, then it is appropriate to migrate all DSOP option 1 areas to DSOP option 4 and all DSOP option 2 areas to DSOP option 5.

Changing the space option does not affect the loaded status of the data area and is effective immediately following its change in the CXX. Because the empty block index was not maintained in the past for basic and wraparound modes, we recommend that, when changing to a DSOP 4 or 5, you run a RETIX KEYNAME=*DATA to rebuild the space index, including the new empty block component of the space index.

Note: You are not required to run this RETIX.

DBUTLTY OLREORG Report Example Change

If the DSOP area is 4 or 5, the line is: Empty blocks used.

The line displays a count of the number of empty blocks to which rows were moved during the OLREORG. The following is a sample of this report:

Rows processed -                        5,000  
Rows moved -                            2,512  
Blocks freed in reference group -       2,510  
Exclusive control conflicts -               0  
Empty blocks used -                         5

If the DSOP area is 0, 1, or 2, the line is: No empty blocks used due to DSOP.

Note: A DSOP of 3 is not supported by OLREORG.

The following is a sample of this report:

Rows processed -                        5,000
Rows moved -                              284
Blocks freed in reference group -         284
Exclusive control conflicts -               0
No empty blocks used due to DSOP               

External Limits

If there are no more blocks in the empty block index, OLREORG uses the next available overflow (NAO) block. OLREORG never causes a dynamic extend.