SAP HANA 2 SPS 04 provides a new feature called SAP HANA Native Storage Extension (NSE). NSE is a disk-based extension to the in-memory COLUMN STORE in SAP HANA. Instead of loading a whole column, only the needed pages are loaded into the buffer cache when accessing the data.
SAP HANA
Native Storage Extension (NSE) is a general-purpose, built-in warm data store
in SAP HANA that lets you manage less-frequently accessed data without fully
loading it into memory. It integrates disk-based or flash-drive-based database
technology with the SAP HANA in-memory database for an improved price-performance
ratio.
SAP HANA offers various software solutions to manage multi-temperature
data (hot, warm, and cold), such as DRAMs for hot data and SAP HANA Extension
Nodes, SAP HANA dynamic tiering for warm data, and SAP HANA Cold Data Tiering
for cold data.
Hot data is used to store mission-critical data for real-time
processing and analytics. It is retained continuously in SAP HANA memory for
fast performance and is located in the highest performance (and highest TCO)
storage.
Warm data is primarily used to store mostly read-only data that need
not be accessed frequently. The data need not reside continuously in SAP HANA
memory, but is still managed as a unified part of the SAP HANA database ―
transactionally consistent with hot data, and participating in SAP HANA backup
and system replication operations, and is stored in lower cost stores within
SAP HANA.
Cold data is used to store read-only data, with very infrequent
access requirements. You manage cold data separately from the SAP HANA
database, but you can still access it from SAP HANA using SAP HANA’s data
federation capabilities. This image shows the difference between standard HANA
in-memory storage and the storage offered with NSE:
The capacity of a standard SAP HANA database is equal to the
amount of hot data in memory. However, the capacity of a SAP HANA database with
NSE is the amount of hot data in memory plus the amount of warm data on disk.
Since growth in data volume results in increased hardware
costs, the ability to decouple data location from a fixed storage location
(layer) is one of the key themes of a multi-temperature data storage strategy.
NSE is integrated with other SAP HANA functional layers,
such as query optimizer, query execution engine, column store, and persistence
layers. Key highlights of NSE are:
- A
substantial increase in SAP HANA data capacity, with good performance for
high-data volumes.
- The
ability to co-exist with the SAP HANA in-memory column store, preserving
SAP HANA memory performance.
- An
enhancement of existing in-market paging capabilities by supporting
compression, dictionary support, and partitioning.
- An
intelligent buffer cache that manages memory pages in SAP HANA native
storage extension column store tables.
- The
ability to monitor and manage buffer cache statistics via system views.
- The
ability to support any SAP HANA application.
- A
simple system landscape with high scalability that covers a large spectrum
of data sizes.
- An
advisor that collects object access statistics and provides column store
object load unit recommendations.
Note:
- The
NSE feature in SAP HANA does not require you to modify your applications.
- Although
SAP HANA 2.0 calculates 10% of memory for the buffer cache by default,
this memory is only reserved and not allocated. SAP HANA accesses 100% of
its memory (including the 10% reserved for the buffer cache) if you are
not using NSE.
- If
there are page loadable tables in your current version of SAP HANA and you
move to another, later, version, only those tables that were designated as
page-loadable in the earlier version use the buffer cache in the later
version (up to the limit that was calculated in the original version of
SAP HANA you were running).