Downgrading Grid Infrastructure from to

In the last article, we performed downgrade of Oracle RAC Database from 12c to 11gR2. In this article, we are going to downgrade Oracle Grid Infrastructure from 12c ( to 11gR2 ( which contains two nodes ( node 1 & node 2). Before doing CRS downgrade we need to take backup of following files : Take tar […]

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Downgrading a RAC database from to

In the last article, we performed downgrade of Oracle Standalone Database from 12c to 11gR2. In this article, we can downgrade the 2 node RAC database to, downgraded the database only and not the grid home. Assume all commands are being run on node 1, any commands that need to be run on node 2 […]

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Downgrade Oracle Database from 12c to 11gR2

We have already upgraded Oracle Database11gR2 to 12c, the whole process is still relatively smooth, although some of the previous version of the upgrade is not the same, but the overall difficulty is not too large, because of too many different features, greatly extended the upgrade time. But for Oracle 12c back to the previous […]

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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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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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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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ORA-16179 incremental changes to “log_archive_dest_10” not allowed with SPFILE

You might encounter ORA-16179 error while changing the archive destination.

There is syntax error in above command . It should be like log_archive_dest_n [n is a integer from 1 to 31]=’LOCATION=path_for_archive_log’ example :

Thank you for giving your valuable time to read the above information. If you want to be updated with all […]

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Recover a datafile from copy

Let’s recover if some datafile is unavailable. Let’s delete users01.dbf datafile which is in USERS tablespace.

Let’s try to create a table name A in tablespace Users.

We need to restore and recover the datafile. Restore means copy from backup, recover means applying changes since the backup is taken.

Restore datafile:


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