What is redo log groups Oracle?
What is redo log groups Oracle?
What Is the Redo Log? The most crucial structure for recovery operations is the redo log, which consists of two or more preallocated files that store all changes made to the database as they occur. Every instance of an Oracle Database has an associated redo log to protect the database in case of an instance failure.
How do I drop a redo log group?
To drop specific inactive redo log members, use the ALTER DATABASE statement with the DROP LOGFILE MEMBER clause. The following statement drops the redo log /oracle/dbs/log3c. rdo : ALTER DATABASE DROP LOGFILE MEMBER ‘/oracle/dbs/log3c.
How many redo log groups are required by Oracle?
Multiplexing the redo log: It is not required that redo log groups be symmetrical, but Oracle recommends that your groups all have the same number of members. A database must have a minimum of two redo log groups.
How do I create a redo log group in Oracle 11g RAC?
i.e a 2 node RAC will have 2 threads. So while adding redolog group, we need to mention the thread parameter….Multiplex redolog in Oracle RAC
- Current redo log status:
- Add logfile groups for node 1 :(THREAD 1)
- Add logfile groups for node 2 : (THREAD 2)
- Drop the old redolog groups:
What is DB_CREATE_ONLINE_LOG_DEST_1?
The DB_CREATE_ONLINE_LOG_DEST_1 and DB_CREATE_ONLINE_LOG_DEST_2 parameters set the default file system directories for redo log file and control file creation. Each redo log file and control file is multiplexed across the two directories. Creating a database.
What is a redo log group?
Redo log groups record all changes made to the database. If an instance or database fails, redo log groups make it possible to reconstruct the database as well as protect rollback segments. Rollback segments store the most recent changes as undo information.
How do you add more redo log groups?
To create a new group of redo log files, use the SQL statement ALTER DATABASE with the ADD LOGFILE clause. The following statement adds a new group of redo logs to the database: ALTER DATABASE ADD LOGFILE (‘/oracle/dbs/log1c.
Where can I find redo logs?
The V$LOGFILE view can be used to find the datafiles for the redo logs. SVRMGR> select * from V$LOGFILE; GROUP# STATUS MEMBER —— —— —————————— 1 /t01/oradata/MYDB/redo.
What is difference between archive and redo log?
Archive logs are archived redo(online) log files. In redo log files are all changes that happened to your data. If your database is in archivelog mode, than redo logs can’t be overwritten, they are archived in some other location when they are full. Redo and archive logs are used in various database recovery scenarios.
What is Db_recovery_file_dest?
DB_RECOVERY_FILE_DEST specifies the default location for the flash recovery area. The flash recovery area contains multiplexed copies of current control files and online redo logs, as well as archived redo logs, flashback logs, and RMAN backups.
What is OMF file in Oracle?
Oracle Managed Files (OMF) directly manages file creation and deletion at the operating system level. Oracle internally uses standard file system interfaces to create and delete files as needed for the database structures such as tablespaces, online redo log files, and control files.
How do you increase the size of the redo log?
select group#, status from v$log; You may have to run the alter command up to three times to get group 1 to be CURRENT. Repeat steps 1 to 7 for group 2, group 3, and group 4. Confirm the size change to each group is now 165 Mb.
How to create new redo log groups in SQL?
For example, adding groups to a redo log can correct redo log group availability problems. To create new redo log groups and members, you must have the ALTER DATABASE system privilege. A database can have up to MAXLOGFILES groups. To create a new group of redo log files, use the SQL statement ALTER DATABASE with the ADD LOGFILE clause.
How to drop inactive redo log members in Oracle?
To drop specific inactive redo log members, use the ALTER DATABASE statement with the DROP LOGFILE MEMBER clause. The following statement drops the redo log /oracle/dbs/log3c.rdo: When a redo log member is dropped from the database, the operating system file is not deleted from disk.
How to create a redo log in alter database?
Online redo logs can be created in multiple disk groups, either implicitly in an initialization parameter file or explicitly in an ALTER DATABASE…ADD LOGFILE statement. Each online log should have one log member in multiple disk groups. The file names for log file members are automatically generated.
How are redo logs created in Oracle ASM?
The file names for log file members are automatically generated. All partially created redo log files, created because of a system error, are automatically deleted. For example, if there are disk groups named data1 and data2, you can create a log file with a member in each disk group with the following SQL statement: