All About REDO LOG

ADD and DROP online redo log members and groups EASY WAY

Redo log Files: The redo log files record all changes made to any data in the database buffer cache except direct writes.

Redo log files are used in instance failure to recover committed data that has not been written to the data files. The redo log files are only used for database recovery.

Online Redo Log Groups

These are the sets of identical copies of online redo log files. The background process LGWR concurrently writes the same information to all online redo log files in a group if a group has more than one log file. The Oracle server needs a minimum of two online redo log file groups for the normal operation of a database. Although oracle suggests keeping three groups.

Online Redo Log Members

These are the members of online redo log groups. Each member in a group has identical log sequence number and of the same size. The log sequence number is assigned each time the server starts writing to a log group to identify each redo log file uniquely. The current log sequence number is stored in the control file and also in the header of all data files.

Obtaining Information about Groups and Members:

The following query returns information about the online redo log file from the control file:

SQL> select group#, sequence#, bytes, members, status from v$log;

The following query returns information about all members of a group:

SQL > select * from v$logfile;

How to “ADD” Online Redo Log Groups : Adding groups can solve availability problems. To create a new group of online redo log files use the following command:

ALTER DATABASE ADD LOGFILE (' DATAFILE_LOCATION/redo03.log') size 1M;

ALTER DATABASE ADD LOGFILE GROUP 6(' DATAFILE_LOCATION /redo06.log')SIZE 50M;

How to “ADD” Online Redo Log Members: Add new member to an existing redo log file group using the following command:

ALTER DATABASE ADD LOGFILE MEMBER ‘ DATAFILE_LOCATION /redo03.log' TO GROUP 1,
' DATAFILE_LOCATION /redo03.log' TO GROUP 2;

How to “DROP” Online Redo Log Groups : To drop a group of online redo log files use the following command:

ALTER DATABASE DROP LOGFILE GROUP 3;

How to “DROP” Online Redo Log Members: To drop a member of an online redo log group use the following command:

ALTER DATABASE DROP LOGFILE MEMBER
‘ DATAFILE_LOCATION /redo03.log';

Happy to Help.

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How to delete/remove Management Agent from Oracle Enterprise Manager 12C

1. Before you deinstall a Management Agent, do the following: a. Stop the Agent using command from Management Agent home: cd /u01/oemcc_latest/core/12.1.0.2.0/bin/ $ emctl stop agent b. Wait for the Management Agent to go to the unreachable state in the Cloud Control console. c. It is mandatory to delete the Management Agent and their monitored targets using any of the following methods: Remove the Agent target manually from the console: 1. Login to 12C Cloud Control 2. Navigate to Setup => Manage Cloud Control => Agents 3. Go to the Home page of the Agent that you want to remove 4. Expand the drop-down menu near the " Agent " 5. Expand the " Target Setup " option 6. Select " Remove Target " ...

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