SQL Execution Statistics -- 1 : A Quick Introduction
A couple of quick examples of how to obtain SQL Execution Statistics using the GATHER_PLAN_STATISTICS HintHere's how you get the Statisitics for an SQL executed from the same session. SQL> Run...
View ArticleSQL Execution Statistics -- 2 : SQL_ID from a Tracefile
In my previous blog post, I have demonstrated sql execution statistics for the last SQL statement of the current session.However, you can trace SQL execution in the current session or in any other...
View ArticleSQL Execution Statistics -- 3 : Using STATISTICS_LEVEL
In my previous posts here and here, I have shown how to use the GATHER_PLAN_STATISTICS Hint to collect additional information. But what if you can't modify the SELECT query statement ?You could set...
View ArticleSQL Execution Statistics -- 4 : Adaptive Plans
In the previous 3 blog posts, I have shown how you can use the GATHER_PLAN_STATISTICS Hint or the STATISTICS_LEVEL='ALL' to get sql execution statistics.This may work with Adaptive Plans as...
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A Fresh Look at AWR Reports -- 1 : CPU Usage
I have covered AWR Reports (from 10g to 12c, including MultiTenant) in the past. You could search for "AWR" in the "Search this Blog" in the panel on the right or by specifying :...
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A Fresh Look at AWR Reports -- 2 : Redo Size
In my previous blog post, I showed how to interpret CPU Usage from an AWR report.Here, I take the same 2hour AWR report and help interpret Redo Size -- ie. volume of Redo Generated and Written to...
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A Fresh Look at AWR Reports -- 3 : I/O Profile
After viewing CPU Usage and Redo Size statistics, here's a look at the I/O Profile.Here's the header which indicates that this AWR report is for duration of 2hours on 19c on Windows :Instead of the...
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A Fresh Look at AWR Reports --- 4 : SQL*Net Waits
After the first three posts on CPU Usage, Redo Size and I/O Profile, I present my interpretation of SQL*Net waits.From the same AWR Report as the first three reviews, I have extracted the specific...
View ArticlePDB Flashback in 21c
Oracle 21c allows you to Flashback a Pluggable Database to a past point-in-time / SCN.Here is a quick demo (also with alert log messages from the Primary and Standby) :On the Primary :SQL> create...
View ArticlePDB Recovery Isolation in 21c
In my previous blog post, where I demonstrated PDB Flashback, I had alluded to the "PDB Recovery Isolation" feature of 21c.Here is a demonstration.On the Primary, I issue only two commands to create a...
View ArticleIndex Statistic NUM_ROWS excludes Rows with NULL value
A quick demonstration of the difference between the Table Statistic NUM_ROWS and the Index Statistic NUM_ROWSSQL> desc customers Name Null? Type...
View ArticleThe format of the ROWID
A ROWID is a method of identifying the physical location of a row in an Oracle Database. An Index on a Table captures the ROWIDs for the rows holding the index key values and these entries in the...
View ArticleDirect Path Insert into a Partitioned Table
Normally a Direct Path Insert that is not committed blocks other concurrent Direct Path Inserts. This behaviour also extends to Partitioned Tables.UPDATE : Correction to 3 lines explaining how the...
View ArticleDirect Path Inserts and Locks
In my previous post I had demonstrated how a Direct Path Insert in one session blocks another Direct Path Insert from another session, except when the two sessions explicitly name separate target...
View ArticleQuerying across a Database Link
In this demonstration, assume that I have a local table called "TARGET_DATA" with a list of Countries and Products. A new company is being acquired and that organisations's product list has been...
View ArticleSCN Synchronization when using a Database Link
In my previous blog post about querying across a Database Link, I had stated "when running a query (just a SELECT statement) requires the two databases to synchronise SCN. Whichever is the database...
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View ArticleRecent Video PlayLists
I've added a few videos to my YouTube Channel in the past two years.Oracle MultiTenant Database ConfigurationsOracle DataGuard
View ArticleThe FILTER operation for an EXISTS query
Let's assume a business case where we want to track customers who have ever placed orders with us.(The business case could be extended to identify customers who have registered with us at least 3...
View ArticleRestoring a PDB from another CDB can increase your SCN
I start with a 19c CDB called "ORCLCDB" and PDB "ORCLPDB1" that is present in it.SQL> col name format a16 SQL> select dbid, name, current_scn from v$database; DBID NAME CURRENT_SCN ----------...
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