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Expert Oracle Posts

Performance Tuning Basics 2 : Parsing

From performance tuning perspectives, it is very important to understand the concept of parsing. Parsing is primary phase in the SQL execution. It is followed by other stages: Execute and Fetch.

PARSING BASICS:

Whenever a SQL statement is executed, Oracle Engine performs below actions on it:

  1. Validate the Syntax
  2. Validate the objects being referenced in the statement
  3. Privileges assigned to user executing the Job
  4. Verifying if statement is already available in the shared pool. Oracle engine will calculate the hash value for the SQL statement and look in
  5. If statement is not already present then allocate shared memory and create a cursor in shared pool
  6. Generate the Execution Plan

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Oracle EXPDP/IMPDP (DATAPUMP) Monitoring Scripts

Usually we monitor the EXPDP/IMPDP jobs by monitoring the log files generated by expdp/impdp process.  Also we monitor alert log too just in case some error pops up. This helps most of the time. If you have a long running expdp/impdp sessions as you are exporting/importing huge GBs then it helps to have a more detailed monitoring of the expdp/impdp jobs. Some of the useful queries which can be used to monitor the  Data Pump Jobs are mentioned below.

To start with some of the important tables/views that you should refer to monitor Data Pump Jobs are:

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EBS Database Parameter Settings Analyzer

All Oracle Apps DBA must have referred below Note id at least once in their career. Most of us refer it  during installation and upgrade of Oracle EBS
application to verify if we have right set if database parameters defined for the optimum performance of EBS application.

Database Initialization Parameters for Oracle E-Business Suite Release 12 (Doc ID 396009.1)

This document has all the required database parameters which are common to all the database release and which are required by EBS application. It also contains release specific database initialization parameters for different releases like 10g, 11g, 12c etc.

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Connecting Oracle Database and SQL Server – Basic Concepts

It is required sometime to connect oracle database to SQL Server database using uni-direction or bi-direction methods. Since these are two different database so something as simple as direct DBLINK will not work here. Below are the basic concepts of making connection from SQL SERVER to Oracle and vice-versa.

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“Wait for a undo record” OR “Wait for stopper event to be increased” database wait events

We faced a scenario in our database where users were complaining about database performance. Database seems to be hanging and queries were either stuck or not running at all.

It was also seen that UNDO tablespace consumption was increasing.

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The Applications File Server could not open the file for read in Oracle EBS

One of our EBS R12 instance was giving below kind of errors when users were trying to open the log and out files of Concurrent requests from EBS front end.

“The Applications File Server could not open the file /fs01/logs/appl/conc/log/l106163221.req for read”

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