Delayed AREA_EXTENT_TRACKING message after directed extend

Document ID : KB000016672
Last Modified Date : 14/02/2018
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Introduction:

Customer is experimenting the new CA Datacom/DB 15.1  AREA_EXTENT_TRACKING n option

Question:

Based on a couple of tests, I am not seeing the new AREA_EXTENT_TRACKING message (DB02827W following a directed extend. In the case I let the test go a bit longer, I eventually saw the relevant AREA_EXTENT_TRACKING message AFTER a subsequent dynamic extend, to a different area in the same base: 


08.59.46 STC30832 DB15MUS1:DB01311I - DYNAMIC_EXTEND 3054,CMI,50,CYL 
08.59.46 STC30832 DB15MUS1:DB01335I - CONSOLE SCHEDULED - DYNAMIC_EXTEND 3054,CMI,50,CYL 
08.59.46 STC30832 DB15MUS1:DB01705I - DYNAMIC EXTEND START CMI3054 CYL 30 DATACOM.DB12.DB3054.CMI 
08.59.49 STC30832 DB15MUS1:DB01706I - DYNAMIC EXTEND END CMI3054 CYL 80 TPNS03 VOL 1 VOLS 1 EXT 2 CYL +50 
09.00.28 STC30832 DB15MUS1:DB00133W # JOB OPEN CM3054A 72169 DEAEOYS JOB90399 XCF-USCD 
09.00.29 STC30832 DB15MUS1:DB01705I - DYNAMIC EXTEND START I033054 CYL 2 DATACOM.DB12.DB3054.I03 
09.00.32 STC30832 DB15MUS1:DB01706I - DYNAMIC EXTEND END I033054 CYL 4 TPNS00 VOL 1 VOLS 1 EXT 2 CYL +2 
09.00.32 STC30832 DB15MUS1:DB02827W # AREA_EXTENT_TRACKING 3054 I03 STARTING EXTENT 2 REMAINING 0 EXPECTED 14 
09.00.35 STC30832 DB15MUS1:DB02827W # AREA_EXTENT_TRACKING 3054 CMI STARTING EXTENT 2 REMAINING 0 EXPECTED 14 


My test system is very current on maintenance...... 

Environment:
z/os, CA Datacom/DB 15.1
Answer:

Note that dynamic extend processing runs to add tracks to a data set. It knows not if those tracks are ever used. They are simply available for some future need. 

The extent tracking has no knowledge of how extents came to be, just when it adds row one to an empty block and that block is the first in an extent, then the message is done to let users know that the extent is now being used to contain data. 

So with the normal dynamic extend because old extents are full it naturally happens that a ADDIT will shortly use the new extend just added. With a directed dynamic extend, it might be minutes, hours, days, forever before an ADDIT needs to use the new extent.

Additional Information:

See documentation:

https://docops.ca.com/ca-datacom/15-1/en/administrating/ca-datacom-db-database-and-system-administration/using-the-multi-user-facility/modifying-muf-startup-options/area_extent_tracking-n