The primary function of the redo log is to record all the changes made to data. Changes made to entries are written to the on-line redo log files. So that they can be used in roll forward operations during database recovery.
When a change has happened, the entry will be first stored in the SGA. SGA has the following components:
1. Shared pool
2. Database buffer cache (DB cache)
3. Redolog Buffer
4. Large pool
5. Java Pool
Shared pool, consists of shared SQL area and shared PL/SQL area. DB cache will have the most recently used blocks & the blocks that needs to be written to the datafile. Redolog Buffer contains the changed/redo data and Large pool is used only in parallel sever environment.
The SGA may also use a Java pool, if java stored procedures are used.
When a SQL statement is executed, the output (data) will be stored in these DB cache as dirty blocks, and then moved into redo log buffers, which will be updated at a later stage.
No comments:
Post a Comment