RE: Block dump - Uncommitted TXN - Help Urgent

  • From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxxxxx>
  • To: <Christian.Antognini@xxxxxxxxxxxx>, "BN" <bnsarma@xxxxxxxxx>
  • Date: Thu, 21 Sep 2006 11:24:02 -0400

Also, note that possibly in 10.1, definitely in 10.2, MAXTRANS is
desupported.  (It's there, but it doesn't actually limit the number of
ITL slots, only free space limits how many slots you can have.)

-Mark 


--
Mark J. Bobak
Senior Oracle Architect
ProQuest Information & Learning

"A human being should be able to change a diaper, plan an invasion,
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die gallantly. Specialization is for insects."   --Robert A. Heinlein



-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Christian Antognini
Sent: Thursday, September 21, 2006 11:03 AM
To: BN
Cc: oracle-l@xxxxxxxxxxxxx
Subject: RE: Block dump - Uncommitted TXN - Help Urgent


Hi
 
> Yes I saw  Request=4 for quite a few sessions. I ahve Identified the 
> Tables that needs INITRANS Bump. Is there a way to figureout  how much

> should I bump for each table in question

If you really experience ITL waits I'm not aware of THE method to
correctly size these stuffs... I'll probably do it in this way...

1) I would find out if the problem is due to MAXTRANS or to free space.
In fact Oracle should dynamically allocate additional ITL slots if
necessary, provided you have free space in the blocks *and* MAXTRANS has
not been reached. 

2a) If the problem is MAXTRANS, i.e. if the number of ITL slots has not
been (unnecessarily) limited, then there are two possibilities:

- Increase MAXTRANS.
- Increase INITRANS.

If there are few ITL waits (few means that the ratio between the number
of DML and the waits is small, e.g. few percent) the former is probably
better.
If there are lots of ITL waits, i.e. INITRANS is way too small, the
latter is probably better.

2b) If the problem is free space, then there are two possibilities:

- Increase PCTFREE.
- Increase INITRANS.

To choose between these two the same method as before can be used.


Note: IMHO is often better to set MAXTRANS to a high value and increase
PCTFREE of 1 or 2 percent instead of setting INITRANS to very high
values.


HTH
Chris
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