Re: what is the difference between share locks and exclusive locks?
- From: Mladen Gogala <mgogala@xxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Thu, 1 Apr 2004 22:59:48 -0500
The difference between shard and exclusive locks is very well described
in Andrew Tannenbaum's "Modern Operating Systems". Oracle uses share lock
on the table level when the foreign key column isn't indexed. For each
update of the parent key column, the whole child table is locked in
the share mode. Apparently, that doesn't improve concurrency, may be
because share-rows-exclusive mode is incompatible with the shared lock
mode. Tannenbaum or Deitel (Operating Systems) are your prescription for
the next weekend.
On 04/01/2004 10:46:07 PM, Ryan wrote:
> Also, other than when you do not index a foreign key, where does oracle use
> share locks?
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Mladen Gogala
Oracle DBA
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