Killable Processes in Oracle Database

A multiprocess Oracle database uses some additional processes called background processes. The background processes perform maintenance tasks required to operate the database and to maximize performance for multiple users. Mandatory Background Processes Optional Background Processes Slave Processes There are few processes which we can kill without terminating the instance. Killable: ARCn: Redo log archivers CJQn: Job […]

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Oracle Internals – Fixed Objects – Part 1

Dynamic Performance Views Oracle contains a set of underlying views that are maintained by the database server and accessible to the database administrator user SYS. These views are called dynamic performance views because they are continuously updated while a database is open and in use, and their contents relate primarily to performance. Although these views […]

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Difference Between Virtual Index and Invisible Index

Virtual Index Virtual indexes allow us to simulate the existence of an index and test its impact without actually building the actual index. Only sessions marked for Virtual Index usage will be affected by their existence. Their creation does not affect new sessions. Virtual indexes will be used only when the initialization parameter “_use_nosegment_indexes” is […]

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Virtual Index or Fake Index in Oracle

Oracle has come up with a feature called virtual index in oracle 9i. This feature allow us to test an index on a table without actually adding an index on the table. The table will be visible only in our session and will be used by our queries only (if optimizer decide it to use). […]

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What happens in the background in Rebuild Index

I must thank my fellow DBA Franky Weber Faust for his publication in his blog. I’ll show you what happens during an online rebuild of an index. Few DBAs realize this, but during this operation an auxiliary index (among other things) is created to store the transient data while the application continues to run normally. Note that for […]

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Create an Oracle SQL TUNING TASK with DBMS_SQLTUNE

You can create an SQL TUNING TASK manually adhoc with the following simple steps. Step1: Find the sql_id of the oracle session you would like to analyze. Usually the AWR has the top sql_ids. In case this is a current sql running use the v$session.

Step2: Login as SYSTEM (or any other user) at […]

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How to extract SQL from SQLT

SQLTXPLAIN gets installed into separate schema called SQLTXPLAIN. It can be installed on RAC and on any version greater than 9i. When it is installed, it will ask for application schema so make sure that installation schema has SELECT_CATALOG_ROLE privilege. In order to run the script to create SQLTXPLAIN schema, one need to connect as […]

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Create Database using DBCA silent mode

DBCA is great tool to create database using GUI , but sometimes when we don’t have access to GUI, we can still create database using DBCA silent mode creation where you need to pass silent option with dbca and some parameter values to create database. In following example we have used template General_Purpose ,   […]

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ESTIMATE in Oracle Expdp

The value for parameter ESTIMATE  is either BLOCKS (default) or STATISTICS. BLOCKS: The estimated space used is calculated by multiplying the number of database blocks used by the target objects with the appropriate block sizes. It is  the least accurate because of: The table was created with a much bigger initial extent size than was needed for […]

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ESTIMATE_ONLY in Oracle Expdp

This parameter is useful when you wanted get the approximate size of the dump file. Suppose you have only limited space available in the disk and if you wanted to check whether your dump will be fit into the available space then you can use this parameter to check or estimate the size of the […]

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