SAP BW BEx Characteristics
This section describes the characteristics of SAP BW BEx data sources:
| • | Quantity of Metadata |
| • | Introspection and Query Behavior |
| • | Search Behavior |
| • | Back-end File Preparation |
| • | Maximum Cells |
| • | BW Statistics Tables |
Quantity of Metadata
Large data sources with complex schemas and big tables with many columns have correspondingly large amounts of metadata, which can have significant impact on TDV performance. For TDV, the most important factor affecting performance is the amount and complexity of metadata that defines the data source, particularly during introspection. For additional information on how to use TDV when introspecting large data sources, see the TDV User Guide.
TDV examines the TABLE-COLUMN relationships in the metadata and queries the data dictionary for full column names.
Introspection and Query Behavior
| • | Time-Dependent Hierarchies—No introspection or SQL changes are required to use time-dependent hierarchies. The adapter uses the default settings for each hierarchy in a query, such as its version and effective date. |
| • | Multiple Structures in Columns Axis—TDV projects two or more structures onto the columns axis. Before TDV version 7.0, the adapter flattened multiple structures projected on the rows axis, but assumed a single structure (typically Key Figures) on the columns axis. |
TDV tables display technical names of the variable from BEx Query Designer. Users are only exposed to the final value in reports, calculated from an input (prompt) parameter. The correct data is returned, but query developers might prefer to alias the column name to a friendlier one in a TDV View.
| • | Maximum Cells—Maximum Cells is an internal proprietary value that is passed from the BEx Adapter directly to BW. It appears to limit the number of cells processed by BW in preparing a result, but in fact Maximum Cells controls the amount of resources that SAP BW uses for a query. Maximum Cells can be set to a value greater than its defaul value of 500,000. |
Search Behavior
In the SAP BEx adapter’s introspection UI, the Search box does not work the way it does for most other data sources.
The BEx adapter loads nodes on demand. Initially, if you search for a BEx query, you get no hits, because nothing has been navigated yet. All TDV knows at this point is the list of top container names.
To see queries, you must pick a top level container, navigate down to a folder containing BEx queries, and expand this folder. Those objects are now indexed and searchable.
To make other queries searchable, you need to go back to the top and drill down another folder path and expand that list of BEx queries. TDV can return BEx queries from all paths you have navigated from top level to query folders.
Back-end File Preparation
A back-end properties file (introspection.properties) containing customer-defined variable values is needed for introspection of BEx queries. If a BEx query cannot be introspected, try again after setting up this file with default values for any variables the query might need. Default values enable TDV to configure the BEx query’s state correctly to obtain its metadata.
The location of this file is:
<TDV_install_dir>/apps/dlm/app_ds_sapbwbex/conf/
Each input parameter in this file has one line with the query’s technical name, the input parameter name, and its literal value. For example, for a query named QRT7_D2_GMT_008 and its five variables, you would use:
QRT7_D2_GMT_008.QRT7ABC=NONE
QRT7_D2_GMT_008.QRT_D2_RUNIT=BG0007
QRT7_D2_GMT_008.QRT7DEFG=ISOLATED
QRT7_D2_GMT_008.QRT7HJK=STRICT
QRT7_D2_GMT_008.QRT7LMN=LOLD
The assigned values just need to be plausible default values. They do not need to be exact for the query to execute.
Those values are used even during normal queries, unless values are provided for required variables. The BEx query is in an invalid state and cannot be executed if required variable values are not provided.
The file is designed to provide values in “unattended mode” (that is, during introspection). In normal queries, you should explicitly provide values for your variables rather than relying on the introspection.properties file.
Maximum Cells
Maximum Cells is an internal parameter of the SAP BW RFC that TDV uses when retrieving cells from an open query. The BEx Adapter simply passes the value to SAP BW.
Maximum Cells limits the resources that SAP uses to execute a query and retrieve results. It is not an upper limit on the result set, like LIMIT in SQL.
BW Statistics Tables
The BEx Adapter calls an extra RFC to cause SAP to write statistics to the OLAP statistics table, mirroring the behavior of the BEx Analyzer. These statistics help the user to understand query performance characteristics before queries are allowed to run on production systems.