Discussion

[sachin kapse]

What are redo log files & latches in oracle

[HGN]

Hi

Looks like you have posted in the wrong forum, this is a Unix forum (HPUX), someone might have details you can also try oracle discussion.

Rgds

HGN

[Peter Godron]

Hi,
In short:

redo logs are files where uncommited changes are written as part of a two-phase commit process i.e. changes are held there until the commit is issued.


latches are holds of data-structures in the SGA whilst the process is using them.

For further reading on latches:
http://oracle.ittoolbox.com/documents/peer-publishing/latches-and-latch-contention-2371

[Sean Dale]

Just in case you were wondering, once redo log rotations are full, they are archived. That is what archivelogs are. Archivelogs are used to restore/undo information, if needed. They are also transferred to standby databases to keep them in sync if you are using dataguard.

[Jonathan Fife]

Hi,

A follow up to Peter's response -- the redo logs actually hold both committed and uncommitted data. If you lose a group of un-archived redo logs you will almost certainly lose committed data, so it is important to multiplex them across physical locations.