gc buffer busy waits

From: <lyallbarbour_at_sanfranmail.com>
Date: Wed, 09 Mar 2011 13:47:08 -0500
Message-Id: <8CDACA1872F5659-1F78-4B7E_at_web-mmc-d03.sysops.aol.com>

Not sure if this has been asked, but i just don't know what to do with the information that ADDM and ASH reports give me.

We have a large table DA.ST_INV_ITEMS_HS, almost 690,000 rows. Big table with lots of columns. The table takes up 632Meg. It has only 173 extents. 8k block database 10gR2 RAC 2 node cluster. Tons of cluster waits on that table. I always thought that that means that one session has queried off this table, locked those blocks or extents in memory on one node and a session on the other nodes is waiting for those blocks or extents to be unlocked.

can someone explain what the ASH report means about Top DB Objects?

Top DB Objects

 With respect to Application, Cluster, User I/O and buffer busy waits only.

Object ID
% Activity

Event
% Event

Object Name (Type)
Tablespace

54768  

17.04  

gc buffer busy  

8.80
DA.ST_INV_ITEMS_HS (TABLE)   USERS         gc cr multi block request  

7.70      

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Received on Wed Mar 09 2011 - 12:47:08 CST