Understanding the persistence layer

SAP HANA's persistence layer manages logging of all the transactions in order to provide standard backup and restore functions. Both the row stores and column stores interact with the persistence layer. It offers regular savepoints, and also logging of all database transaction since the last savepoint.

The persistence layer is responsible for the durability and atomicity of transactions. The persistence layer manages both data and log volumes on the disk, and also provides interfaces to read and write data that is leveraged by all the storage engines. This layer is built based on the persistency layer of MaxDB, SAP's traditional relational database. The persistency layer guarantees that the database is restored to the most recent committed state after a restart, and these transactions are either completely executed or completely rolled back. To accomplish this efficiently, it uses a blend of write-ahead logs, shadow paging, and savepoints.

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