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? > ---------------------------------------------------------------- > Please see the official ORACLE-L FAQ: http://www.orafaq.com > ---------------------------------------------------------------- > To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx > put 'unsubscribe' in the subject line. > -- > Archives are at //www.freelists.org/archives/oracle-l/ > FAQ is at //www.freelists.org/help/fom-serve/cache/1.html > ----------------------------------------------------------------- > -- Mladen Gogala Oracle DBA ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at //www.freelists.org/archives/oracle-l/ FAQ is at //www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------