Logical File Names 

Use

In order to save data in a file in the cache modes Main Memory Cache with Swapping, Flat File Cache per Application Server and Cross-application Server (see Cache Mode), the following specifications must first be set:

·        Definition of the logical file path and assignment of a platform-specific physical path.

·        Definition of the logical file name

From the Cache Monitor screen, using  Logical File Names, you can access the complex table maintenance for logical file paths and -names. The table maintenance consists of several sub-dialogs (views). SAP has already delivered a proportion of the required settings.

You need to check these settings and make any adjustments necessary for your file system before you can use the persistent OLAP cache with a flat file as a background store.

Note that these assignments are subject to settings made for the transport connection. (You need a request that can be transported).

Features

The following section gives an overview of the sub-dialog in the table maintenance using an example configuration. For more information about the procedure in detail, see Defining Logical Path- and File Names.

You can choose the following sub-dialogs via the Dialog Structure:

Logical File Path Definition

The (platform-independent) logical file path is evaluated at runtime to get the (platform-dependent) physical path (see Assignment of Physical Paths to Logical Path).

Two examples of this are:

·         Logical file path: BW_OLAP_CACHE

Name: BW OLAP Cache

·         Logical file path: BW_OLAP_CACHE_SPAN

Name: BW OLAP cache cross-application server

Assignment of Physical Paths to Logical Path

At runtime, the physical path assigned for the corresponding operating system platform is generated from the logical file path.

Since the physical path is platform-dependent, the customer must set it her/himself. The closer the file is to the application server or, with the cross-application server cache mode, to the application server, the faster it can be found and read.

Log(ical) path: BW_OLAP_CACHE

Name: BW OLAP Cache

Syntax group: UNIX (all Unix platforms)

Phys(ical) path: /usr/<SYSID>/global/<FILENAME> (You can choose the path up to <FILENAME> according to your own configuration.)

If you cannot find the syntax group for file names and paths for your operating system, you can define your own (see Syntax Group Definition and Assignment of Operating System to Syntax Group).

The parameter <FILENAME> must always be set for the physical file name (see Logical File Name Definition, Cross-Client). At runtime, the complete platform-specific file name is automatically constructed from the physical path and the physical file name.

Logical File Name Definition, Cross-Client

At runtime, a complete platform-specific file name including the path is generated for a (platform-independent) logical file name.

In the following example, cache data is stored on an application server:

Logical file: BW_OLAP_CACHE (we recommend you use the delivered attributes for the logical file).

Name: BW OLAP cache files

Phys(ical) file: CACHE_<HOST>_<SYSID>_<PARAM_1>

Data format: BIN (binary)

Application area: BW (Business Information Warehouse)

Logical path: BW_OLAP_CACHE (see Logical File Path Definition). Input help is available.

In the following example, cache data is stored cross-application server:

Log(ical) file: BW_OLAP_CACHE_SPAN

Name: BW OLAP cache cross-application server

Phys(ical) file: CACHE_<SYSID>_<PARAM_1>

Data format: BIN

Application area: BW

Log(ical) path: BW_OLAP_CACHE_SPAN

Make sure that a particular schema is stipulated for the physical file name:

·        For application server storage (see Global Cache Parameters and Cache Mode Main Memory Cache with Swapping and Cluster / Flat File Cache per Application Server):

CACHE_<HOST>_<SYSID>_<PARAM_1>

·        For cross-application server storage (see Global Cache Parameters and Cache Mode Cluster / Flat file Cache Cross-application Server):

CACHE_<SYSID>_<PARAM_1>

The following table offers an overview of the variables that are only replaced with actual values during run time:

Variables in physical file names

Variable	Meaning
<HOST>	Computer-/server name (for SY-HOST). This variable is not required if the data is stored cross-application server
<SYSID>	System ID This variable serves to differentiate systems if, for example, two different BI systems are running on one application server, so that they do not over-write each other
<PARAM_1>	External parameter 1 (sequence number in HEX)

Defining Variables

If you want to use variables in physical file names and –paths, you can define these via New Entries.

Syntax Group Definition

If required, you can define a new syntax group for operating systems with the same syntax for file names and paths via New Entries.

Syntax grp: UNIX

Name: All Unix platforms

Length (of file name)

Extension: Choose this option if the data format for the logical data name is allowed to be the file name extension for this syntax group

Active: Choose this option if the operative system for this syntax group is used in the available system configuration.

Assignment of Operating System to Syntax Group

If required, you can assign your operating system to a syntax group via New Entries.

OP system: SunOS

Name: SUN Unix