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Status Not under consideration
Workspace Db2
Created by Guest
Created on Feb 12, 2015

RELATED IDEAS

Turn on reclaimable storage without dropping/recreating the tablespaces

After a migration from db2 9.5 to 10.1, several days passed, and we reached the maximum size of a DMS tablespace of 4K.



We moved one table to a different tablespace, but still noticed that the free pages were equal to 0.



We tried to execute the alter tablespace with the option reduce max and found that the space was not reclaimable:



db2 "SELECT varchar(tbsp_name, 30) as tbsp_name, tbsp_type, RECLAIMABLE_SPACE_ENABLED FROM TABLE(MON_GET_TABLESPACE('',-2))"



TBSP_NAME TBSP_TYPE RECLAIMABLE_SPACE_ENABLED


------------------------------ ---------- -------------------------


SYSCATSPACE DMS 0


STEMP04K01 SMS 0


USERSPACE1 DMS 0


DATA04K01 DMS 0


INDEX04K01 DMS 0


UTEMP04K01 SMS 0


LONG32K01 DMS 0


SYSTOOLSPACE DMS 1


DATA16K01 DMS 1


STEMP16K01 SMS 0


NADATA04K01 DMS 1


NAINDEX04K01 DMS 1


INDEX04K02 DMS 1


DATA04K02 DMS 1


LONG32K02 DMS 1


DATA04K03 DMS 1


INDEX04K03 DMS 1



17 record(s) selected.



We asked the db2 specialist about this limitation, but it seems there is no way to change this attribute dynamically.



We have around 400 databases which were migrated from version 9.5 to version 10.1, this implicates such a huge amount of work if we need to drop and recreate the table spaces in order to make this feature available for them.



Reference: http://www-01.ibm.com/support/docview.wss?uid=swg21438047

  • Guest
    May 27, 2025

    Hi Siji Daniel,
    there still a lot of tablespaces out there, which have been carried through various versions of Db2 as databases are migrated and not recreated. So the problem is still present even in 11.5 or 12.1.
    Have you ever tried to lower a tablespace HWM for an old (pre V9.7 created) tablespace, which by accident got altered to AUTOMATIC STORAGE? With that move you never can get that TS reduced again, as AS assumes the TS must have reclaimable storage.
    The old way by reducing the HWM doesn't work, as it's declared as automatic storage now. But the new REDUCE MAX (e.g.) fails, as the TS is NOT reclaimable! So you are stuck and have to create a new TS, move all the data over there (using e.g. admin_move_table procedure) and drop the old TS. But this means you need twice as much storage until you can DROP the old TS.
    So making an existing old TS reclaimable w/o drop/create of that TS would be a great relief.

    Reply
  • Admin
    Siji Daniel
    May 26, 2025

    The idea describes an issue on tables created on very old versions of Db2 (pre-v9.7). Storage may be reclaimed quickly with ALTER TABLESPACE command to reduce and lower high watermark or other functions to rebuild indexes and tables online. Marked as Not Under Consideration as it is no longer applicable.

    Reply

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