Backup and recovery introduction

 what is persistence layer?

persistence layer is required to ensure that the HANA system can be restarted or restored back to the last consistent state in case of a power failure or abrupt shutdown or system failure.

    Database data is stored 2 places:

         1. Data volumes.
         2. Log volumes.


1.Data volume:

    It contains system data, Application data and undo logs
    it write data in Async mode.

    

2. Log volume:

Redo logs store the changes to the data (insert, update , Delete).

Synchronous writes on commit.

Savepoint: changed data and undo logs are written from memory to disk.

                     default every 5 minutes

                     Automatic execution.

to take complete backup of system, need 3 things:

1.  Complete backup.
2.  incremental / differential backups.
3. Most recent log entries from the log area.