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Use

By pressing Cache Parameters, you can change the settings for the OLAP cache.

Integration

The global cache parameters are set centrally during implementation of the BW system.

Note

For more details, see the Implementation Guide (IMG) for SAP NetWeaver → SAP NetWeaver Business Warehouse → Performance Settings → Global Cache Settings.

Features

Cache Inactive

If you set this parameter, the global cache is deactivated centrally. Note that this option impairs the performance of all queries throughout the system.

Local Cache Size in MB

You use this parameter to set the size of the local cache. This limits consumption of memory caused by the cache at query runtime.

Tip

If a value of 50 MB is set here for example, the query will collect no more than this amount of cache data at runtime.

The local cache is still also used in certain cases, for example:

  • If the global cache has been deactivated (see the Cache Inactive parameter).
  • If the cache has been deactivated for the InfoProvider (for all future queries) or the query (see Cache Mode)
  • When it turns out at runtime that caching cannot take place (see Technical Information under Cache-Relevant Data: Query Can Use Cache)

Global Cache Size in MB

You use this parameter to set the size of the global cache in the main memory. This parameter therefore only affects cache modes Main Memory Cache with/without Swapping (cache modes 1 and 2 - see Cache Modes). If you are using a database cache (cache modes 3, 4, 5), there is no size restriction. Accordingly, this parameter is not relevant for any of these modes.

Tip

As the global cache has to take the memory objects of each local cache of all query instances, the size of the global memory cache should be set significantly larger than the local cache.

A further restriction of the global memory cache is caused by the fact that it is physically stored in the shared memory. The size of this buffer therefore sets the maximum possible size of the global main memory cache.

Tip

As the shared memory is also used by other applications as cache, it should be at least 102400 kB (100MB) instead of the default size 4096 KB (4MB). As a system administrator, you can set the size of the buffer in Profile Parameter Maintenance (transaction RZ11, parameter rsdb/esm/buffersize_kb).

Persistence mode

You use the persistence mode to set whether and how form cache data is stored in non-volatile storage media, like file systems or databases.

Cache mode 5 Query Aggregate does not have its own persistence mode. Instead it automatically stores the cache entries with query data in a cluster table or a BLOB store (table with XSTRING area). More information: Cache Administration Parameters.

The following information relates to the older cache modes 2-4, which are not defaults and are only provided to ensure compatibility (see Cache Modes).

Cache Mode 2 Main Memory Cache with Swapping

The Persistence Mode parameter determines what happens to the data in the cache if the memory reaches its maximum size. Part of the data has to be displaced - i.e. removed from the main memory - or moved to the database in a file (flat file) or as a BLOB or cluster table. A process using the Least Recently Used (LRU) algorithm determines which data is affected by this.

Cache Modes 3-4 Persistent Cache per Application Server or Cross-Application Server

The persistence mode parameter specifies whether the data is stored in a file (flat file) or a database table.

The following table offers an overview of how the available persistence modes can be used:

Persistence Modes for Cache Modes 2-4

Persistence mode Cache Mode Main Memory Cache with Swapping Cache Modes Persistent Cache per Application Server or Cross-Application Server

Inactive

Once the cache memory has been used up, data is deleted from the memory (corresponds to cache mode Main Memory Cache Without Swapping).

Flat file

When the memory space available for caching has been exhausted, the data is archived in a file.

Flat File Name: Logical file path that flat files are stored under.

The cached data is stored as a file in a directory on the application server or cross-application server in the network.

Flat File Name: Like in cache mode Main Memory Cache with Swapping

Cross-File: Logical file path that the data is stored under. The path is not dependent on the application server

Database Table:

  • Cluster Table
  • Transparent Table (BLOB)

Once the cache memory has been used up, data is stored in the database in a non-transparent cluster table or in a transparent table with BLOB (Binary Large Object).

The cached data is stored in the database as a non-transparent cluster table or as a transparent table with BLOB (Binary Logical Object). Cluster tables differ in whether they have the application server in the key. This depends on the cache mode

Note

If your selection is initial (blank), the system sets the persistence mode to inactive and displays this accordingly on the OLAP Cache Monitor screen under Cache Parameters.