How “Write operation” works in Hana? What is “Delta Merge Operation”?

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Hana Data Structure has two components namely Main Storage & Delta Storage.

Data StructureAccess PatternCompression
Main StorageOptimized for read accessAdvanced
Delta StorageOptimized for write accessBasic
  • Read operations are performed on both structures, while write operations only affect the delta.

Main Storage

The main storage contains the main part of the data (data compression).

Delta storage

Write operations on compressed data in the main storage would however be costly. Therefore, write operations do not directly modify compressed data in the main storage. Instead, all changes are written to a separate data structure called the delta storage.

The delta storage structure itself exists only in memory and is not persisted to disk.

Delta merge Operation

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

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