144. What is On-line Redo Log?

The On-line Redo Log is a set of tow or more on-line redo files that record all committed changes made to the database. Whenever a transaction is committed, the corresponding redo entries temporarily stores in redo log buffers of the SGA are written to an on-line redo log file by the background process LGWR. The on-line redo log files are used in cyclical fashion.

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sandeep vig

Oct 13th, 2005

The online redolog is a set of minimum two filegroups which has minimum one member and oracle uses it to record all the changes made to the database whether it is commited or not commited.oracle uses it to perform recovery after database crash.

venkat

Feb 10th, 2006

all un-commited transactions are stored in the redo logs

diliph
Profile Answers by diliph

Aug 2nd, 2007

Online Redo Log files are those which contain the information that changed the datafile, it contains both the commited and uncommited data aswell. These files are needed for recovery.

samala

Sep 15th, 2007

Redo logs records all the changes to the database whether commited or uncommited. How does it know whether you are committing or rolling back till you commit it. Oracle always thinks positively that everything is going to be commited and writes to the log and when it is rolled back, it rolls back from the rollback segment otherwise those segments will be used for another transactions. Please correct me if iam wrong.

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Naveen samala

oracleofdelphi
Profile Answers by oracleofdelphi

Sep 9th, 2009

Online redologs name is used since archivelogs are called offline redologs. Online redologs can be in three states current to which lWr is currently writing transaction changes then this current becomes active after it gets filled and logswitch/ckpt happens then active becomes inactive only after its contents are syncronized with corresponding datafiles and undo files after this step it becomes inactive and it can go to current state only from inactive mode since this is a cycle its called cyclic buffer.