RE: Dba_tab_modifications question

Precisely :)

• Kirti

-----Original Message-----

Sent: Thursday, May 16, 2002 9:23 AM
To: Multiple recipients of list ORACLE-L

So DBA/ALL/USER_TAB_MODIFICATIONS cannot be used to determine an accurate count of how many records were updated, but it can used to determine if the table has been updated, and give you a general feel of how much has been updated.

AND is used by the GATHER STALE parameter in DBMS_STATS.GATHER_SCHEMA_STATS to determine which tables have been updated, and therefore may have stale statistics and need to have their stats refreshed.

With these features setup you can basically throw away your nightly "analyze everything" process and use a more intelligent approach. Very cool.

-----Original Message-----

Sent: Wednesday, May 15, 2002 9:28 PM
To: Multiple recipients of list ORACLE-L

True, there is such a latch (so, Gopal is right :) However, this latch is to protect the hash table structure where these modification counts are kept.
The updating of these counters is still done without acquiring any other latches (so, John is right :)
Also, a transaction can be rolled back, but the affected modification counts from this hash table can not be rolled back. So the modification counts can be different due to rolled back transactions and updating counters without latch protection (as John explained).

Cheers !

• Kirti

-----Original Message-----

Sent: Wednesday, May 15, 2002 6:18 PM
To: Multiple recipients of list ORACLE-L

John:

Not being so choosy, MONITORING is subject to latching. There is a latch called 'hash table allocation/modification latch' which keeps the modification in the shared pool and SMON periodically flushes to the disk.

Best Regards,
K Gopalakrishnan
Bangalore, INDIA

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