Original Post can be viewed at Poll on Sql Plan Management

Dominic is conducting poll on SPM and Sql Profiles usage on his website. Link can be found here  I have been using SPM and SQL Profiles (using coe_xfr_profile.sql) to fix plans for queries  and believe me its very easy and quick way of fixing problems in production database. I have not yet used SPM to [...]

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Original Post can be viewed at Optimizer Choosing Nested-Loop Joins Instead of Hash-Joins

In one of my databases, one application query suddenly started to pick Nested-Loop joins instead of Hash-Joins and took almost 6 hours to complete which gets completed in less than 10 secs with Hash-Joins. The same query in another similar database with same configuration and same data is doing fine and using hash joins. There is [...]

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Original Post can be viewed at User Sessions stuck on resmgr:cpu quantum wait event

We were experiencing lot of session getting stuck on resmgr:cpu quantum in our database. In fact at a time we had 70 sessions which were stuck on this wait event and our cpu load average was touching 60 Checking active resource plan, we found that DEFAULT_MAINTENANCE_PLAN was active. As per 11g Docs In this plan, [...]

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Original Post can be viewed at Plan Stability using Sql Profiles and SQL Plan Management

PLAN STABILITY How many times you have noticed a query using Index X when you wanted it to use index Y or query performing Nested Loop join when Hash Join would have completed the query much faster.Or take a scenario when the application suddenly starts using wrong plan after database restart. To solve all these [...]

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Original Post can be viewed at V$SQL_SHARED_CURSOR in 11.2.0.2

Oracle 11.2.0.2 has introduced new column “REASON” to V$SQL_SHARED_CURSORS. I came across this extremely useful column while debugging multiple child cursor issue (11.2.0.2 seems to have too many bugs which can cause multiple child cursors). As per documentation , REASON column has been introduced in 11.2.0.2 REASON - CLOB Child number, id, and reason the [...]

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Original Post can be viewed at Oracle Database Appliance Introduced

Oracle has introduced it new product: ODA (Oracle Database Appliance) I was not able to join Oracle President Mark Hurd’s webcast where he supposed to announce a new Oracle product[It was at 1AM my time and I was sleeping], now viewing this webcast HERE Kerry Osborne has shared information about this product, click link to [...]

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Original Post can be viewed at Performance Management Guide on AIX

While trying to find the amount of physical memory used by oracle process on AIX, I got reference of a document from Metalink: Performance Management Guide It tell us about which process is using how much memory and how to interpret the output of commands like: vmstat, svmon, ps on AIX. Also, to get more [...]

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Original Post can be viewed at ORA-01722 with Full Table Scan

My application developers approached me with an issue which is very unique to me. They were complaining about a query which was failing with ORA-01722 “invalid number” after an upgrade to 11.1.0.7 from 10.2.0.4. The syntax of the query is like: select max(a) from t1 where c1<>'abc' and c2=12345 and c3='Y' and c4='xyz'; This query [...]

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Original Post can be viewed at October 2010 Blogroll Report

It’s been time since we saw log-buffer edition with last being published on 1st October 2010 and  Coskan’s weekly blogroll report I found them really useful to read top blog articles for week. So I decided to tag few articles posted in October 2010 which I  had read and found useful. I am subscribed to [...]

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Original Post can be viewed at Sqlplus connection on AIX taking too long

Recently we faced a performance issue, where in sqlplus connection from application server A (AIX 5.3) to Database server DB (different physical server,10gR2 on AIX 5.3) was taking nearly 1-2 minutes.  We did some quick check’s to narrow down the problematic area.i.e Is it network or database server or some issue with application server? 1)Vmstat [...]

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Original Post can be viewed at GATHER_STATS_JOB – Is it enabled?

Few days back , Martin had posted a series of post on a issue where GATHER_STATS_JOB was failing silently for a large object. If you have missed it, you can check following links Automated statistics gathering silently fails http://mwidlake.wordpress.com/2009/07/20/automated-statistics-gathering-silently-fails/ Automated Statistics Gathering Silently Fails #2 http://mwidlake.wordpress.com/2009/07/23/automated-statistics-gathering-silently-fails-2/ Automatic Statistics Gathering Fails #3   http://mwidlake.wordpress.com/2009/07/29/automatic-statistics-gathering-fails-3/ Automated statistics [...]

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Original Post can be viewed at Mview Complete Refresh and Atomic_refresh parameter

This post discusses issue faced by me while working on Materialized view (mview) creation at new site(database). Starting Oracle 10g, how atomic_refresh works with complete refresh has undergone a change. Atomic_refresh parameter is to allow either all of the tasks of a transaction are performed or none of them (Atomicity). If set to TRUE, then [...]

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Original Post can be viewed at dbms_stats.copy_table_stats does not alter low/high value

I was working on a performance issue arising due to missing table stats on a new partition for large Partitioned table.This was a 10.2.0.4 database on IBM AIX 5L. So as to resolve the issue , I used dbms_stats.copy_table_stats to copy the stats to new parition from the previous partition. EXEC DBMS_STATS.COPY_TABLE_STATS (‘owner’, ‘tabname’, ‘SourcePart’, [...]

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Original Post can be viewed at You Don’t need SysDBA privilege to run Awrrpt..

Well I tried to Sensationalize this post by using such a heading Though I just wanted to point out that Awrrpt script can be run without sysdba privilege too. Actually if you open awrrpti.sql script , it contains following line Rem NOTES Rem Run as SYSDBA. Generally this script should be invoked by awrrpt, Rem [...]

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Original Post can be viewed at Connections to DataBase Hang Including “/ as sysdba”

Recently I faced one issue where all the connection to database hung and it was also not possible to login to database using “/ as sysdba”. To get access of sqlplus I used the following syntax: $ sqlplus -prelim / as sysdba With “prelim” option we can run some commands which will help in collection [...]

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Original Post can be viewed at Index Access best approach?? Not Always…

There is a common misconception that Index access is the best access method for query execution. This approach leads to people concentrate on removing Full Table Scans (FTS) from the Query execution plan. I recently worked on a performance tuning issue where I found such scenario. Basically customer was trying to generate report for 3 [...]

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Original Post can be viewed at Resolving Shutdown Immediate Hang Situations

Many times Oracle DBA’s are faced with a situation where shutting down the instance with shutdown immediate seems to take infinite time and gives a impression that the session is hung. In most of the cases this is not a hang. Hang can be defined as a scenario when few sessions/processes are waiting on some [...]

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Original Post can be viewed at Tracing Sessions with Event 10046

10046 Event is used to trace SQL statements (similar to sql_trace=true) with additional details depending on the tracing level which is specified. 10046 EVENT levels: 1 – Enable standard SQL_TRACE functionality (Default) 4 – As Level 1 PLUS trace bind values 8 – As Level 1 PLUS trace waits 12 – As Level 1 PLUS [...]

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Original Post can be viewed at Sign on Letter to Larry Ellison on AWR and ASH Licensing

While surfing across the blog’s, I found this particular link, a compaign which is aimed at getting free access to the ASH and AWR reports. I believe most of us know that we need to pay extra fees for the Diagnostic Tuning Pack which also includes ASH and AWR report. (If you’re not already familiar [...]

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Original Post can be viewed at HW enqueue contention with LOB

DefinitionEnqueues are local locks that serialize access to various resources. Enqueue wait event indicates a wait for a lock that is held by another session (or sessions) in an incompatible mode to the requested mode. HW Enqueue – High Watermark enqueue is acquired when a segment’s high water mark is moved, which will normally happen [...]

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