Re: Help with Locking Issue

This is hugely irritating, and I guess it may be a version-dependent thing, but I can't get the exact match for the quoted locks by setting up three tables in the manner described.

The locking information varies between 8.1.7.3 and 9.0.1.3, but I can't get a PK/FK issue to behave (mis-behave ?) properly.

Various failures include:

1. Seeing a lock on the parent table
2. Not seeing the TX mode 4 (share) lock at all
3. See a TM mode 5 (share row exclusive) request on the child. (combined with a held mode 3 (row exclusive).

Which version of (exact) Oracle is this, and have you figured out the exact pattern of actions that make the problem appear.

My tables are:

    P1 (id_p1 number primary key ...)
    P2 (id_p2 number primary key ...)
    C(id_p1 references P1, id_p2 references P2, primary key (id_p1,id_p2) ...)

This seems to describe your scenario - two foreign keys, but only one of them index by virtue of the composite primary key.

Jonathan Lewis
http://www.jlcomp.demon.co.uk

Author of:
Practical Oracle 8i: Building Efficient Databases

Next Seminar - Australia - July/August
http://www.jlcomp.demon.co.uk/seminar.html

Host to The Co-Operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html

-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 18 April 2002 19:45

I had already checked that, but since you asked, I double checked. The primary key on the FIXED_ASSET_ACTIV table has two columns - both are foreign keys from other tables. I created a separate index for the 2nd column in the PK. This fixed my problem!

So, the foreign key was indexed, it just wasn't indexed correctly.

Thanks,
Jay

>>> <Scott.Shafer_at_dcpds.cpms.osd.mil> 04/18/02 01:17PM >>>
Jay, do you have any unindexed foreign keys on those tables? If so, Oracle
>
> Sess Op Sys OBJ NAME or
> ID USERNAME User ID TERMINAL TRANS_ID TY Lock Mode
Req
> Mode
> ---- -------- ---------- -------- ----------------- -- -----------
> -----------
> 12 KEN468 ken468 KEN468-1 FIXED_ASSET_ACTIV TM Row Excl
> 12 KEN468 ken468 KEN468-1 Trans-196694 TX Exclusive
> 14 KEN468 Batch BATCH FIXED_ASSET_ACTIV TM Row Excl
> 14 KEN468 Batch BATCH Trans-196694 TX --Waiting--
Share
> 14 KEN468 Batch BATCH Trans-65597 TX Exclusive
>
>
> So session 14 is waiting for a share lock. Session 12 has an
exclusive
> lock that is blocking session 14. How do I find out what session 12
has
> locked that is needed by session 14?
>

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Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

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