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Wait for unread message on broadcast channel

unread message on broadcast channel

When using data pump you will have a calling session which is the session that you log into the DB with when executing the impdp or expdb utility. Within the DB there will be one or more sessions which are called by this main data pump session; namely DWn. Where N is a number.

I was recently using data pump to complete a “cutdown” environment of our PROD DB for a development environment. I was using data pump because it gives such a fine level of control for this task and allows for greater control in terms of what is imported into the DB. Anyway, I had imported all of the schemas I wanted and the table structures, procedures, constraints, etc and I wanted to import the data. So I ran the impdp command to import just the data I had selected using the expdp, but for some reason it was hanging. I delved deeper into what was going on and I saw that the wait events for the sessions were “Datapump dump file I/O” and “wait for unread message on broadcast channel”.

I’ve seen the “wait for unread message on broadcast channel” previously, and this was because there was a tablespace which was 100% full; data pump didn’t error, it just hung but the alert log told me what was happening, so it was easy to fix. I digress…so I used some tracing to see what was going on in the database:

exec dbms_system.set_ev(2181, 94, 10046, 12, ”)

The statement above turns 10046 tracing on for the specified session at level 12.

This turned out to be because there was a trigger on one of the tables and it continued to fire and fail.

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Category: Data Pump


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