Results 1 to 6 of 6
  1. #1
    Join Date
    Mar 2005
    Posts
    73

    Unanswered: Lock-wait threads

    UDB V8.1 FP5
    OS : Solaris.


    I am seeing some connections going to Lock-waits while an online backup is being performed.

    While the online backup is going on a few connections are trying to accesses a table in IX mode . And these connections are getting timed off after some time with 911 error code with 68 reason code.

    I have identified the table which theese connections are trying to access.
    And the mode too.

    How do i resolve this problem. So far i thought that while the online backup is perofrmed , applications can connect to the database and perform updates.

    Isn't it correct.

    thanks

  2. #2
    Join Date
    Aug 2001
    Location
    UK
    Posts
    4,650
    When an online backup is performed, the first step is to backup the catalog tablespace. To ensure consistency, the backup application takes a share lock on all catalog tables.
    There are certain operations, like LOAD, RUNSTATS, DDLs etc, that tend to take an X-lock on a row(s) of the system catalog tables. Naturally, such applications will timeout when the catalog is being backed up or the backup may fail if such operations are in progress ...

    This is more a timing issue ... I have worked around this by having a retry logic in runstats and/or backup scripts and scheduling the conflicting operations to happen at different times ...

    Does this explain your problem or are you seeing something different ???

    Cheers

    Sathyaran
    Visit the new-look IDUG Website , register to gain access to the excellent content.

  3. #3
    Join Date
    Mar 2005
    Posts
    73
    The table which is being requested for IX mode by the applications is not system catalog table. It is an application table.

    THe backup has a Share lock on this table. At that time the application(s) are requesting IX mode on that table.

    And after a couple of minutes the applications are getting timed off.

    How do i resolve this problem. How do i implement a retry logic.
    I am thinking it is more of application code issue.

  4. #4
    Join Date
    Aug 2001
    Location
    UK
    Posts
    4,650
    Any chance it is a table in SMS tablespace with LOB data ?

    Sathyaram
    Visit the new-look IDUG Website , register to gain access to the excellent content.

  5. #5
    Join Date
    Mar 2005
    Posts
    73
    yes.

    It got a BLOB column.
    BLOB(2097152) LOGGED NOT COMPACT .


    But this table is in DMS tablespace . But i see that this table with BLOB column was created in regaular tablespace of page size 4k.

  6. #6
    Join Date
    Mar 2005
    Posts
    73
    Any inputs ..from any one..


    thanks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •