Re: tempspace usage

A 10046 trace should show direct path reads/writes when the session starts sorting/hashing to disk. Also check the SEGTYPE column to see if the space is being used for sort, hash or temporary tables/indexes.

If the problem is the space doesn't disappear from V$SORT_USAGE across multiple statements, I'd bet it was temp tables/indexes because a sort or hash should disappear when the statement ends while the temp table persists until the end of the transaction or session depending on how its scope was declared. The join to V$SQLAREA as has been suggested won't help in this case because the V$SORT_USAGE.SQLADDR doesn't point anywhere since no single SQL statement "owns" it. I've never been able to effectively been able to map such a row back to a particular temp table/index just using the data in V$SORT_USAGE.

If there's only one statement and it keeps running and running, allocating space the entire time, it's the culprit. There's lots of reasons for this: Massive hash join, ORDER BY on a massive result set (like a cartesian product), really big GROUP BY, etc.

S-

On Tue, 19 Apr 2005, Greg Norris wrote:

> Is there a way to determine (or trace) which individual statements are
> causing tempspace to be allocated to a session? I've got a databases
> where half a dozen sessions seem to gradually allocate more and more
> tempspace (as measured by v$sort_usage), and then never release it.=20
> Eventually they acquire almost all of the available space, which of
> course causes a flurry of ORA-1652 errors from other sessions.
>
> At the moment, I'm examining a trace from one of these sessions. So
> far, I don't see anything which could cause this behaviour... a few
> inserts, some relatively simple selects, nothing particularly complex.
> Any suggestions on how to troubleshoot this sort of issue?
>
> The DB in question is Oracle 8.1.7.4.0 (32-bit), running on Solaris 8.

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Stephen Rospo        Principal Software Architect
Vallent Corporation (formerly Watchmark-Comnitel)
Stephen.Rospo_at_vallent.com           (425)564-8145

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