RE: How do commits release row level locks?

From: Anjo Kolk <anjo_at_oraperf.com>
Date: 16 Feb 2004 13:25:17 +0100
Message-Id: <1076934317.6429.5.camel@redhat.famkolk.com>

To answer them:

initrans will allocate the slots, maxtrans will only limit youif the space is available. If there is no space left in the block, you will only have the ITL entries that you specified by initrans.
The wait for an TX enqueue is 3 seconds in this case. So oracle waits 3 seconds, wakes up checks a couple of things and goes back to sleep if it didn't get the enqueue. So that is why you see the 3 seconds.

Anjo.

On Mon, 2004-02-16 at 13:10, Naveen, Nahata (IE10) wrote:
> Hi All,
>
> Can someone please explain me why the following happens:
>
> Step 1. CREATE TABLE TEMP (COL1 NUMBER) PCTFREE 0 INITRANS 2 MAXTRANS 3
> Step 2. INSERT values from 1 to 100,000 in the table
> Step 3. COMMIT
> Step 4. Since the insert was sequential, I assume the values 1, 2, 3, 4, 5
> should be in the same block (I can test the same using rowid as well)
> Step 5. From one session issue "DELETE TEMP WHERE col1 = 1"
> Step 6. From the second session issue "DELETE TEMP WHERE col1 = 2"
> Step 7. From the third session issue "DELETE TEMP WHERE col1 = 3"
> Step 8. The third session waits on "enqueue". This is understandable since
> PCTFREE is 0 and the block has no space to create a third ITL Slot.
> Step 9. ROLLBACK the second session. This should release the ITL Slot (???)
> Step 10. Still the third session waits on "enqueue". Should it not go ahead
> with the delete now that one transaction has rolled back?
> Step 11. ROLLBACK the first session and the delete issued by the third
> session goes ahead.
>
> I tried the same experiment with INITRANS set to 3, and the fourth session
> hangs, and doesn't move ahead until all the other three session rollback or
> commit. It seems that the waiting session doesn't go ahead until all the
> sessions have finished their transactions.
>
> Moreover, when I look at V$SESSION_WAIT, it shows the session waiting on
> "enqueue" and SECONDS_IN_WAIT increment from 0 to 3 and then again get reset
> to 0.
>
> Can someone please explain this? It seems I'm missing something, but what?
>
> 9.2.0.3 on Solaris
>
> Regards
> Naveen
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Received on Mon Feb 16 2004 - 06:25:17 CST