Do I always need redo logs?

Question

hi guys,
Is there a way to turn off redo logs being written to to make the database faster? I am not using ARCHIVELOGS as it is a test database, so I dont see of having any redo logs.
thanks

Answer 1

Hi,
No, You can't turn off the redo logs, Let’s conduct a brief summary about the redo process. When Oracle blocks are changed, including undo blocks, oracle records the changes in a form of vector changes which are referred to as redo entries or redo records. The changes are written by the server process to the redo log buffer in the SGA. The redo log buffer is then flushed into the online redo logs in near real time fashion by the log writer LGWR. (See Figure 1)
The redo logs are written by the LGWR when:
•     When a user issue a commit.
•     When the Log Buffer is 1/3 full.
•     When the amount of redo entries is 1MB.
•     Every three seconds
•     When a database checkpoint takes place. The redo entries are written before the checkpoint to ensure recover ability.
Redo log files record changes to the database as a result of transactions and internal Oracle server actions. (A transaction is a logical unit of work, consisting of one or more SQL statements run by a user.) Redo log files protect the database from the loss of integrity because of system failures caused by power outages, disk failures, and so on. Redo log files must be multiplexed to ensure that the information stored in them is not lost in the event of a disk failure. The redo log consists of groups of redo log files. A group consists of a redo log file and its multiplexed copies. Each identical copy is said to be a member of that group, and each group is identified by a number. The Log Writer (LGWR) process writes redo records from the redo log buffer to all members of a redo log group until the file is filled or a log switch operation is requested. Then, it switches and writes to the files in the next group. Redo log groups are used in a circular fashion.
Best practice tip:
Oracle recommends that redo log groups have at least two files per group, with the files distributed on separate disks or controllers so that no single equipment failure destroys an entire log group.
The loss of an entire log group is one of the most serious possible media failures because it can result in loss of data. The loss of a single member within a multiple-member log group is trivial and does not affect database operation, other than causing an alert to be published in the alert log.
Remember that redo logs heavily influence database performance because a commit cannot complete until the transaction information has been written to the logs. You must place your redo log files on your fastest disks served by your fastest controllers. If possible, do not place any other database files on the same disks as your redo log files. Because only one group is written to at a given time, there is no harm in having members from several groups on the same disk.+
Note: This is a extract of my paper: [Logging or Not Logging, This is the Question.|http://oraclenz.com/__oneclick_uploads/2008/08/redo_reduction_v_1_9.pdf]
I hope this will help you.
Regards,
Francisco Munoz Alvarez
www.oraclenz.com