Sap Hana - Delta Merge Operation

Sap Hana Architecture

About

The Delta Merge Operation is an operation on a table column store data structure.

The purpose of the delta merge operation is to move changes collected in the delta storage to the read-optimized main storage.

After the delta merge operation, the content of the main storage is persisted to disk and its compression recalculated and optimized if necessary.

A further result of the delta merge operation is truncation of the Sap Hana - Table Column - Column Store (ie redo operations)

It is important to understand that even if a column store table is unloaded or partly loaded, the whole table is loaded into memory to perform the delta merge.

During the delta merge operation, every partition of a partitioned table is treated internally as a standalone table with its own data and delta store.

Sap Hana Delta Merge Operation

Management

SQL

MERGE DELTA OF '<table_name>' (hard merge)
MERGE DELTA OF '<table_name>' WITH PARAMETERS ('FORCED_MERGE' = 'ON') (forced merge)
MERGE DELTA OF '<table_name>' WITH PARAMETERS ('MEMORY_MERGE' = 'ON') (memory-only merge)





Discover More
Sap Hana Architecture
Sap Hana - Data Persistence

SAP HANA persists in-memory data by using savepoints operation in data volume (file). Whenever a Savepoint or a Snapshot is created or a delta merge is performed, data is persisted from memory to the...
Hana Column Store Write Read Operations
Sap Hana - Table Column - Column Store

Table column. Data Structure Access Pattern Compression Main Storage Optimized for read access Advanced Delta Storage Optimized for write access Basic Read operations are performed on...



Share this page:
Follow us:
Task Runner