How Do You Calculate Redo Log?

How do you find the number of redo log groups?

To multiplex the redo logs, first, we must identify how many groups and members exist.

Sql> select group#, member from v$logfile order by group#, member; The above query helps to find out the existing groups and members’ information.

For example, if your existing member filename is redo01..

How do I change the size of my 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.

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 would be the rule of thumb regarding an acceptable online redo log switch frequency?

Answer: In a production environment it is important to size your online redo log files to ensure that the frequency of redo log switches is not more than 5 log switches per hour during peak DML activity.

When should I increase redo log size?

As a general rule of thumb, Oracle recommends that you size your online redo logs not to switch more then 5 times per hour during peak DML times.

Where is Oracle redo log file?

The redo log files are initially specified within the CREATE DATABASE command. CREATE DATABASE . . . LOGFILE ‘/t02/oradata/MYDB/redo1.

What is Db_block_size?

The DB_BLOCK_SIZE is the size of the default data block size when the database is created. Since Oracle 10g Release 2, each tablespace can have a different block size, thus making block size selection a less critical selection before the database is created.

How do I change the block size in Oracle 12c?

Use the following workflow to change the buffer cache size to use multiple DB block sizes.Check current available SGA and buffer size. … Try creating a tablespace with block size = 4kb, this fails with following error. … Alter system to add the db_4k_cache_size parameter.More items…•Jun 22, 2016

How do I create a redo log file?

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.

Does MySQL have redo logs?

By default, the redo log is physically represented on disk by two files named ib_logfile0 and ib_logfile1 . MySQL writes to the redo log files in a circular fashion. Data in the redo log is encoded in terms of records affected; this data is collectively referred to as redo.

What is redo log size?

The minimum size permitted for a redo log file is 4 MB. See Also: Your operating system–specific Oracle documentation. The default size of redo log files is operating system dependent.

How do you find the frequency of a redo log switch?

Ideally redo log switch frequency should be 4-5 log switches per hour. If there is frequent log switches then check the size of redo logs and increase accordingly. V$LOG_HISTORY is used to check history of redo log generation in Oracle.

How do I manually use redo logs?

To apply the archived redo logs in the archive gapStart up and mount the standby database (if it is not already mounted). … Recover the database using the AUTOMATIC option: … Cancel recovery after the Oracle database server has applied the available logs, by executing the following statement (or typing CTRL+C):

What is online redo log file?

The most crucial structure for recovery operations is the online 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 online redo log to protect the database in case of an instance failure.

How many redo logs are needed in Oracle?

two redo log filesAn Oracle database must have at least two redo log files, and most databases have more than two. These files are written by the LGWR process in a circular fashion; that is, when the last log file is filled, the first log file is reused.

How do you estimate redo logs?

I discovered that I have 15 groups of 2 GB, so the redo log group size is 30 GB. Oracle says that “In general we recommend adding an additional 30% on top of the peak rate”, so that would mean I am expected to have 245mb/s*1.3 = 318.5 MB/S.

How do I know the size of my redo log block?

The easy way to find redo block size is to get trace of redolog and read that.Below one is done on solaris platform: Dump redolog: … Now check generated trace (it will under the same location where alert log is present) … So redolog block size in this database is of 512 bytes.

How do I restore a redo log file?

To restore archived redo logs: If the database is open, shut it down and then mount it: shutdown immediate; startup mount; Perform the following operations within your run command: If desired, specify the new location for the restored archived redo logs using set archivelog destination.

What are the archived redo logs used for?

Archived redo logs are used to recover a database or update a standby database. Before you restore, you must locate the file. When you locate the files, ensure that the database is in the Open state.

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