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June 2009

Diagnosing and Resolving “gc block lost”

Last week, one of our clients had a sudden slow down on all of their applications which is running on two node RAC environment

Below is the summary of the setup:
– Server and Storage: SunFire X4200 with LUNs on EMC CX300
– OS: RHEL 4.3 ES
– Oracle 10.2.0.3 (database and clusterware)
– Database Files, Flash Recovery Area, OCR, and Voting disk are located on OCFS2 filesystems
– Application: Forms and Reports (6i and also lower)

As per the DBA, the workload on the database was normal and there were no changes on the RAC nodes and on the applications. Hmm, I can’t really tell because I haven’t really looked into their workload so I don’t have past data to compare.

Two weeks to go for ODTUG

ODTUG Kaleidoscoop 2009 is approaching soon. I'll be hosting two presentations.Fat Databases: a Layered ApproachThis will basically be the Helsinki Declaration talk, only crammed into just one hour. I'll probably skip the four observations and go straight to the WoD application and its code classification (DL, BL and UI-code). And close with a short demo by building a page (with Apex of course)

ORA-04031 errors and monitoring shared pool subpool memory utilization with sgastatx.sql

Since Oracle 9.2 the shared pool can be “partitioned” into multiple parts. This was probably done for relieving shared pool latch contention for crappy applications (which use shared pool latches too much due bad cursor or connection management).

The “partitions” are called shared pool subpools and there can be up to 7 subpools. Each subpool is protected by a separate shared pool latch and each subpool has its own freelists and LRU list. If you are interested in more details, a good starting point is this whitepaper by Oracle.

There are few different ways for detecting how many subpools you have in use. The more convenient ones are here:

You could query X$KGHLU which has a line for each shared pool subpool and (from 10g) also java pool if it’s defined:

ORA-04031 errors and monitoring shared pool subpool memory utilization with sgastatx.sql

Since Oracle 9.2 the shared pool can be “partitioned” into multiple parts. This was probably done for relieving shared pool latch contention for crappy applications (which use shared pool latches too much due bad cursor or connection management).

The “partitions” are called shared pool subpools and there can be up to 7 subpools. Each subpool is protected by a separate shared pool latch and each subpool has its own freelists and LRU list. If you are interested in more details, a good starting point is this whitepaper by Oracle.

There are few different ways for detecting how many subpools you have in use. The more convenient ones are here:

You could query X$KGHLU which has a line for each shared pool subpool and (from 10g) also java pool if it’s defined:

Rebound for database design?

My fellow Oaktable member Robyn Sands posted something very "inline" with the Helsinki declaration. Good comments too.