Longops in Oracle

Question

Hi,
I'm using Toad For Oracle and I have found - what I think is - a way to see the longest running operations made recently in our database.
The tab is called longops (found in the Session Browser ). Here Toad gives me a list of
long running operations. In the listing (which I can sort by time taken) I see quite a few full table scans together
with the time taken for each scan.
My first question is - can I trust Toad on this?
The items in the list looks something like:
FULL TABLE SCAN ON <table name>            40 sec.                 2012-04-12  12:00:00            56000 out of 56000 blocks doneMy second question is - what SQL can I use to generate this output?
In Toad - I need to click on a session (user) and then I get the statistics for that session (user).
I would like to get the statistics for all the recent sessions (users).
/best regards, Håkan

Answer 1

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My first question is - can I trust Toad on this?
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Trust Toad on what? Displaying a lot of data like that when you select the session browser tab? Absolutely!
But the important thing is to learn what the data represents, which of the data is meaningful and what is just leftover garbage.
And you should not query that view by itself. See this AskTom blog
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1099233454171
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data in v$session_longops hangs out until those slots are needed for reuse. You should
approach v$session_longops with specific sid,serial#'s -- you do not query the table by
itself. You can join this to v$session or whatnot.
You should ignore rows in there that are not for current sessions. You cannot clear
them.
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As for this
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My second question is - what SQL can I use to generate this output?
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Oracle-base has a large selection of scripts that can be used for analysis and monitoring. This one is for v$session_longops
http://www.oracle-base.com/dba/scripts.php
And this is their main script page
http://www.oracle-base.com/dba/scripts.php
If you are the one writing code that may 'run long' then you should consider having that code create entries in the view
to make identification of your task easier and to highlight what step the task is on.
For this your code would use DBMS APPLICATION INFO.SET SESSION LONGOPS
http://docs.oracle.com/cd/B28359_01/appdev.111/b28419/d_appinf.htm#i996999
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SET_SESSION_LONGOPS Procedure
This procedure sets a row in the V$SESSION_LONGOPS view. This is a view that is used to indicate the on-going progress of a long running operation. Some Oracle functions, such as parallel execution and Server Managed Recovery, use rows in this view to indicate the status of, for example, a database backup.
Applications
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See the example in that section
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This example performs a task on 10 objects in a loop. As the example completes each object, Oracle updates V$SESSION_LONGOPS on the procedure's progress.