How to reduce buffer busy waits, session hanging due to buffer busy waits

Question

Hi,
How to reduce buffer busy waits, session hanging due to buffer busy waits.
Thanks,
Sathis.

Answer 1

When I see through enterprise manager I see lot of
tables with buffer busy waits.
Is there any way by table name we can check the
blocks info.
The simple way is to look at the SQL statement and corresponding table name?
P1=file#, P2=block#. You can extract segment name(table or index) using this info.
Query v$bh like following:
SQL> select file#, block#, class#, objd from v$bh where file# = P1 and block# = P2;
SQL> select object_name from all_objects where object_id = <objd>;See following doc:
http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14237/dynviews_1051.htm
Or you can dump block:
SQL> alter system dump datafie <P1> block <P2>;Some excerpts from block dump:
scn: 0x07df.17e70782 seq: 0x01 flg: 0x04 tail: 0x07822301
frmt: 0x02 chkval: 0x61d0 type: 0x23=PAGETABLE SEGMENT HEADER
Map Header:: next  0x00000000  #extents: 1    obj#: 55881  flag: 0x10000000>
Can we do something at table level that will reduce
the waits.
Yes, some methods are known. But before thinking of that, you must verify which block class and which access are involved.
Typo... always. :(
Message was edited by:
Dion_Cho