OLAP: Cache Monitor  

Purpose

The OLAP Processor accesses two types of cache, the local cache and the global cache.

The local OLAP cache stores the results calculated by the OLAP Processor in the role area for each session. This is based on a single query instance at runtime.

Unlike the local cache, the global OLAP cache is cross-transactional. This makes it possible for various query instances to access the data stored here. This data is optimized for the OLAP Processor. This speeds up execution of the query due to faster access and the fact that the data has already been formatted.

At runtime, all drilldown states of the query – from a given calculation level - are cached locally to start with and then stored globally if required. The entries in the local cache are generated from the local runtime (cache) objects.

Various cache modes are supported for the global cache. These differ in terms of their persistence medium – the storage medium - and in the structure of the cache hierarchy that OLAP Processor uses to locate the individual objects in the cache.

We recommend setting cache mode BLOB/Cluster Enhanced as the standard mode.

The only other cache mode of significance alongside BLOB/Cluster Enhanced is Main Memory Without Swapping (1).

The other cache modes that are actually only offered for compatibility reasons – cache modes (2) to (4) - can be parameterized by setting the administration parameter Use Old Cache (see Cache Administration Parameters). For more information about the old cache modes, see Cache Mode and Technical Information About Old Cache Modes.

The Cache Monitor screen provides you with information about the local cache, the global cache parameters, the amount of memory used by the query runtime objects and the current underlying cache structure.

Integration

●      To make the recommended cache mode BLOB/Cluster Enhanced available in your system, you need to activate a table parameter. Follow these steps:

...

                            a.      Call the Data Browser (transaction SE16).

                            b.      Enter RSADMIN in the Table Name field. The selection screen for this table appears.

                            c.      Enter parameter name RSR_CACHE_ACTIVATE_NEW in the Object field and X in the Value field.

                            d.      Choose   Execute.

●      You can set the standard cache mode for an InfoProvider in Customizing. If you change these settings later, the changes do not affect existing queries for this InfoProvider. They only affect future queries created for this InfoProvider.

●      The cache parameters are set in Customizing during implementation. The same settings can also be made in the OLAP Cache Monitor (see Cache Parameters). To call the OLAP Cache Monitor (transaction RSRCACHE) from the SAP Easy Access screen, choose Business Explorer →  BEx Monitor →  OLAP: Cache Monitor.

●      You can change the cache mode for a query in the Query Monitor screen in transaction RSRT (see Query Properties).

You can access an overview of the cache-relevant data for a query (important time stamps for example) from the Query Monitor screen by pressing  Technical Info (see Technical Information).

From the Query Monitor screen, you can call the OLAP Cache Monitor by pressing  Cache Monitor.

Features

Cache Parameters

Display cache parameters. The display is based on the settings made in Customizing. Example:

	Cache Parameters
	Cache Active
	Local Cache Size	50 MB
	Global Cache Size	200 MB
	Cache Persistence Mode	Cluster Table

Note that these parameters only relate to the main memory cache and not to the database caches.

Choose  Cache Parameter to change any settings. More information: Cache Parameters.

Cache Mode Functions

In addition to the cache parameters, you can also view the relevant data for all cache modes:

Pushbutton	Display
Technical Info	Displays cache-relevant information about the query run-time objects. For main memory cache modes it also displays the buffer status (Shared Memory)
Buffer Objects Hierarchical Display or  Buffer Objects List Display	Displays the buffer objects In the default setting, the system displays buffer objects in a hierarchically structured query directory. More information: Cache Structure.

Other Toolbar functions

The following functions are available in the toolbar:

General Functions

Function	Information
(Refresh)
(Delete)	Deletes the cached data in accordance with the cache mode selected, deleting the buffer objects that you have chosen to display. If no selection has been made, the system does not delete any data. This function is useful when testing. To delete old entries in the cache, we recommend scheduling program RSR_CACHE_RSRV_CHECK_ENTRIES to run in background processing on a regular basis. See Cache Data Removal and Swapping.
Cache Parameter	See Global Cache Parameters.
Admin Parameter	See Cache Administration Parameters.

Functions for cache mode Main Memory Cache with/ Without Swapping

Function	Information
Buffer Monitor	Choose   Buffer Monitor or  Buffer Overview to check whether enough cache memory is available for example. You can use  Buffer Monitor to call the Buffer Monitoring Tool screen, which provides you with an overview of the buffers for your application server. In the Buffer Overview screen area the shared memory rows (buffer: Exp/ImpMem) contain data relevant to the OLAP cache: ·         Size: Maximum size of the cache memory in bytes ·         Free bytes: Free cache memory in bytes ·         Directory: Maximum number of directories (individual packages in the cache memory) ·         Dir. Free: Number of free directories ·         Efficiency: Degree to which requests can be met, in %, - corresponds to the Hit ratio in the Buffer Overview
Buffer Overview	The Tune Summary screen appears (transaction ST02). The shared memory row (buffer: Exp/Imp SHM) contains data relevant to the OLAP cache: ·         Hit ratio: [%]  - corresponds to Efficiency in the Buffer Monitor ·         Allocated: [kB] ·         Free space: [kB] and [%] ·         Dir. size: Entries ·         Free directory: Entries and [%] Note that both the number of bytes and the number of directories have a limiting effect. You can find out which of these values might be critical from the relationship between the respective maximum value and free capacity value. More information: Buffer Monitor.

Functions for the cache modes Main Memory Cache with Swapping (into a file), and the persistence mode with Flat File Cache

Function	Information
Logical File Names	See Logical File Names (transaction FILE).
Directory Overview	The SAP Directories screen appears. DIR_GLOBAL  /usr/<SYSID>/global Double-click on the physical path to call the file display. If you have kept to the naming conventions, you can find your physical file under CACHE_<HOST>_<SYSID>_<PARAM_1> or CACHE_<SYSID>_<PARAM_1>. To find out more about defining logical and physical file paths and names, see Logical File Names.