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Why do I see (blocked) in the sessions view?

by markc » Wed Mar 05, 2014 3:57 pm

I am running a query which does not seem to be doing anything, and when I look in the Status for it in the Sessions view, I see "(blocked)" as part of the status, whether it is Compiling or Running. What does this mean?
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Re: Why do I see (blocked) in the sessions view?

by markc » Wed Mar 05, 2014 4:01 pm

blocked in this context means the query is waiting on a lock.

If you query SYS.IPE_LOCKS you should see your query has one or more lock entries with status PENDING, which means they cannot be granted due to conflicting locks.

Typically this is because other sessions which are actively executing queries are holding conflicting locks, so when they complete their transaction they will release the locks and the blocked query can proceed.

One other way we've seen this happen in the past is if a Console user did "set mode transaction" in a Query tab, and then opened other query tabs to run further queries without realising these tabs all use the same database connection. Hence the transaction mode applied to all of them. To avoid problems of this nature, remember that the query tabs in a Console instance all use the same connection, and hence any state set in one (e.g. transaction mode, current_session parameters) will apply to all of them.
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