Re: ITL Deadlock Example?

It gets more complicated under Oracle 9 because initrans has a minimum value of 2 on tables; but under oracle 8, the following should work:

create table t1
initrans 1
maxtrans 1

insert a few dozen rows into t1
so that there are rows in at least
two blocks, and commit.

session 1

    update a row in block 1
session 2

    update a row in block 2
session 1

    update a row in block 2 -- will wait on a TX/4 session 2

    update a row in block 1 -- will wait on a TX/4

After ca, three seconds session 1 will report ORA-00060.

In Oracle 9, you may get lucky with just two blocks of data and three concurrent sessions, but for consistency you need to have three blocks of data and rotate through the sessions updating one row in each block from each session in turn.

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

|Walter K wrote:
|
|> Can someone post an example of how to trigger a
|> deadlock (ORA-0060) due to ITL shortage? This is for
|> informational/fact-finding purposes.
|>
|> I've created a test table with MAXTRANS=1 and can
|> cause the enqueue waits between two sessions
|> contending for the same block but I can't seem to
|> cause a deadlock to occur.
|>
|> Thanks.
|> -w
|>

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