1. Cursor Sharing Bug: 2138662

2. Bug 2138662: cursor_sharing=force causes ORA-7445 and core dumps related bugs –2195595: production instance crashed with a ORA- 07445 [11] –1358871: cursor_sharing = force causes ORA-7445 (ttcclr) in proc program –2118514: ora-3113 and ORA-7445 [rworirw2()+704] while running a query having order by –1951929: recieving many ORA-7445 [kqrgcu()+244] errors introduced in Oracle 8.1.7.2, some fixed in Oracle 8.1.7.4

3. What is Cursor Sharing? Cursor sharing determines what statements are considered to be identical, and can therefore share the same cursor or cache entry. The statement is rewritten bind variables replacing literals Can be enabled as session level In a badly written application this can avoid excessive parse times.

4. What goes wrong? Heap corruption caused by rewritten statement Associated with ORDER BY clause

5. Workarounds cursor_sharing = exact cursor_space_for_time = true –but sometimes causes ORA-4031 –in which case flush shared_pool frequently

6. Summary The bugs may be different aspects of the same problem cursor_sharing can cause a heap corruption in the shared pool I would suggest that it is not safe to use this feature to deal with poor performance caused by high parse times.

7. David Kurtz Go-Faster Consultancy Ltd. david.kurtz@go-faster.co.uk www.go-faster.co.uk