Standby Database Types in Data Guard ?

In Standby Database are three types

1. Physical Standby 

2. Logical Standby

3. Snapshot Standby

1. Physical Standby:

    

  Physical standby are have three types of  modes ,they are 

                     i. Maximum Protection

                    ii. Maximum Performance

                   iii. Maximum Availiability

   i. Maximum Protection :

            * In Max protection Mode Log writer writes redo entries to standby log file, for that reason                    we require additional Standby logs  in standby database,

           *  If  network  goes down  between primary and standby,Primary and standby is not                                  communicate due to network issue,primary automatically will goes down.

   To Set Max. Protection:

       

       In  Primary Database: 

           1. Put the database in mount.

                 SQL>alter database open;

           2. SQL>alter database set standby database to maximize protection;

           3. open the databse 

                SQL>alter database open;

 ii. Maximum Performance : 

           * In Maximum performance Archive logs will be transfer to primary to standby by Log                          network  Service(LNS).

           * Then this archive logs will be write to the database by MRP process.

          * If any network issue happen in primary and standby,FAL SERVER will monitor the Network               Issue onces it comes up FAL SERVER  send a request to FAL CLIENT  saying that i                           have these  many archives can you please send the remaining one.

  Note: FAL SERVER AND FAL CLIENT  used in order to resolve the archivelog gaps

  iii. Maximum Availiability :

         * In Maximum Avaliability first it behave like a  maximum protection write the redo entries to                Standby,if it fails to write standby logs due to network issue then it will behave like a max.                  performance and send the  archive gs to standby database and MRP process apply this                          archive  to standby database.        

                    

                  

    To set  Primary Database :

       1. put the database mount

       2. SQL>alter database set standby database to maximize availability;

       3. open the database

            SQL>alter database open

       4. To check standby  Database Modes

           SQL> select protection_mode from v$database

2. Logical Standby :

               in READ ONLY state, LSP will run

3. Snapshot standby Database :

Physical standby database can be converted to snapshot  standby database, which will be in  READ WRITE mode, can do any kind of testing, then we can convert back snapshot standby database to physical standby database and start MRP which will  apply all pending archives

                                                         Thank You