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Why after Datacom DEFRAG IXX did percent full continued to decrease?

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Article ID: 201944

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Updated On:

Products

Datacom/DB Datacom/AD

Issue/Introduction

After running DEFRAG to reorganize the index and free up deleted space to my CA-11 base 601, the DATA AREA SPACE UTILIZATION REPORT also known as DBUTLTY "TYPE A" report (DBUTLTY with REPORT AREA=CXX,DBID=601,TYPE=A) decreased the percent full from 96% to 46%.

Then, a rerun of the TYPE A report several minutes later showed the percent continued to decrease to 2%.

Why did the percent continue to decrease with no additional DEFRAG? 

After the DEFRAG, the TYPE A report showed 46% IXX percent full:

DATACOM/AD                   DATA AREA SPACE UTILIZATION REPORT
-AREA DATA       TOTAL           TOTAL       TOTAL        USED    PERCENT    PARTIALLY  AREA REUSE
 NAME BASE      TRACKS         RECORDS      BLOCKS      BLOCKS  FULL   MAX  EMPTY BLKS    OPTION
CXX               250             N/A       3,000         258     8     8         N/A  N/A
IXX   601      16,500             N/A     198,000     92,673   46    96         N/A  N/A
DSN  601      11,250         271,850      78,750       6,982     8     9         261  RANDOM
  JHF  601       1,500               0      10,500           2     0     0           0  RANDOM
  JOB  601       2,475           5,471      17,325         344     1     1           1  RANDOM
  STP  601       2,475          27,352      17,325         601     3     3         103  RANDOM

Then, TYPE A report showed the followed several minutes later showed 2% IXX percent full:

DATACOM/AD                   DATA AREA SPACE UTILIZATION REPORT
-AREA DATA       TOTAL           TOTAL       TOTAL        USED    PERCENT    PARTIALLY  AREA REUSE
 NAME BASE      TRACKS         RECORDS      BLOCKS      BLOCKS  FULL   MAX  EMPTY BLKS    OPTION
CXX               250             N/A       3,000         258     8     8         N/A  N/A
IXX   601      16,500             N/A     198,000       5,001     2    96         N/A  N/A
  DSN  601      11,250         271,850      78,750       6,981     8     9         261  RANDOM
  JHF  601       1,500               0      10,500           2     0     0           0  RANDOM
  JOB  601       2,475           5,471      17,325         344     1     1           1  RANDOM
  STP  601       2,475          27,352      17,325         601     3     3         103  RANDOM

 

Environment

CA Datacom

CA Datacom/DB

CA Datacom/AD

15.1

15.0

Resolution

All index blocks deleted when running a DEFRAG are put on the Index Queue and each block will show up as truly deleted in the IXX report after the index queue processes it.

DEFRAG (Defragment Index)

MUF EOF report provides statistics "REQUEST COMPLETION TASKS" related to index queue processing.

COMM EOJ (End MUF Processing)

Also, X_DEFRAG_DELAY_QUEUE console or startup option allows you to throttle the index queue processing.
"When mass maintenance, especially deletes, to a data area adds very large numbers of blocks to the index queue, it might be beneficial to throttle DEFRAG processing."
X_DEFRAG_DELAY_QUEUE can slow the DEFRAG down so it does not flood the queue, but it is not recommended for situations where the queue finished its processing.

Additional Information

This is working as designed and had been provided as enhancement to CA Datacom.