Re: Weird database hanging

All the symptoms suggest that something is shutting you out of the shared pool - so the comments from other posters about web applications and creating sessions might be highly relevant.

There's a tale of woe here:
http://www.jlcomp.demon.co.uk/kiddy_scripts.html#_Always_be_cautious_about_x$_and_v$ that might be of interest.

If this is relevant, then check the shared_pool_reserved_size. A connection needs a continguous chunk of about 26KB for "session parameters" - so it is a good idea to create a reserve that is set to a minimum of "sessions * 26KB" (plus a few, or few dozen, MB for whatever you currently have in there) so thatthese chunk eventually end up being allocated in the reserve rather than causing a massive flushed on the rest of the pool.

Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http:/www.jlcomp.demon.co.uk

don_at_seiler.us wrote:
> I have opened an SR with Oracle, as it has hung 3 times today and
> actually crashed once.
>
> When the database hang, Ignite is showing "latch: shared pool" and
> "latch: library cache" waits. Otherwise I don't see these at all.
>
> Oracle has had me up OPEN_CURSORS and SESSION_CACHED_CURSORS, but I
> did that last night (with instance restart) and, as I said, it has
> hung 3 times and crashed once since then. Oracle's also telling me
> that this is largely due to application coding. My problem with that
> is that the application code has been in place for a while.
>
> To recap: we migrated to the 64-bit machine on Sep 1. Hanging has
> occurred since Sep 13, seemingly during bulk load activity. Our SGA
> is quite a bit larger (16 GB) than on our 32 bit box (1.5 GB).
>
> db_cache_size big integer 12G
> shared_pool_size big integer 2G
>
> I haven't seen the "block change tracking buffer space" wait since
> yesterday morning, thankfully.
>
> Any tips would be appreciated.
>
> Thanks,
> Don.
>
> --
> Don Seiler
> oracle: http://ora.seiler.us
> ultimate: http://www.mufc.us
>

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