What is the minimum size permitted for a redo log file?

4 MB
The minimum size permitted for a redo log file is 4 MB.

What size should redo log be?

Dell EMC recommends a 512-byte block size for redo log files on ScaleIO.

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.

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.

  1. Below one is done on solaris platform: Dump redolog:
  2. Now check generated trace (it will under the same location where alert log is present)
  3. So redolog block size in this database is of 512 bytes.

What is the difference between redo log and archive 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 does redo log file contains?

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.

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.

How do I restore a redo log?

Recovering After the Loss of All Members of an Online Redo Log Group

  1. Locate the filename of the lost redo log in V$LOGFILE and then look for the group number corresponding to it.
  2. Determine which groups are active.
  3. If the affected group is inactive, follow the procedure in Losing an Inactive Online Redo Log Group.

How many maximum redo logfiles one can have in a database?

The following parameters limit the number of redo log files that you can add to a database: The MAXLOGFILES parameter used in the CREATE DATABASE statement determines the maximum number of groups of redo log files for each database. Group values can range from 1 to MAXLOGFILES .

What to do if archive log is full?

You can also fix this full problem by adding space to your archived redo log directory. For full scripts to monitor and remove archived redo logs, see the book “Oracle Shell Scripting” by Jon Emmons.

What is written in redo log files?

What is difference between archive and redo log?

Which is the best way to size redo logs?

The following SQL will give advice on the optimal size of the redo logs, but manual inspection of redo log switch frequency is always the best approach: Oracle 10g introduced an advisory utility that allows you to specify your optimal mean time to recovery (MTTR) recovery interval and uses this to suggest the optimal redo log size.

Which is the optimal redo log size in Oracle 10g?

Oracle 10g introduced an advisory utility that allows you to specify your optimal mean time to recovery (MTTR) recovery interval and uses this to suggest the optimal redo log size. In Oracle 10g the fast_start_mttr_target parameter is used.

Can a small redo log file cause a slowdown?

A too small online redo log file size can cause slowdowns from excessive DBWR and checkpointing behavior. A high checkpointing frequency and the “log file switch (checkpoint incomplete) can cause slowdowns. – Redo log sizing advisory [MOSC ID 274264.1]

Can a redo log be maintained in multiple locations?

To protect against a failure involving the redo log itself, Oracle Database allows a multiplexed redo log, meaning that two or more identical copies of the redo log can be automatically maintained in separate locations. When setting up a multiplexed redo log, place members of a group on different physical disks.