When we build data model in Oracle OBIEE, We actually use OBIEEs administration tools. A windows client tools that we could
- Define physical layer for real data sources
- Define star schema,dimension hierarchy in the business model and mapping layer
- Define end user s interface through the presentation layer.
The output of these definitions will be saved into a file call BI repository definition (.rpd)
At start up of Oracle BI Server, It will read this rpd file into memory, Whenever user query the data model, BI Server will find in the RPD file for definition of the query against the data model which finally map to the backend data source. BI Server will then generate dynamic sql and send these sqls to different backend data source. After execution, BI Server will also assemble the come back result from the real data sources and construct the required data to the end user.
Here is a snapshot of the BI administration tools that we use to define our data model
Some important BI Server files
These are some important files that used by BI Server
- RPD BI repository definition file which contain definition of physical layer, business model and mapping layer and presentation layer.
- NQSConfig.ini BI Server configuration file, the most important configuration is a path to the RPD file.
Star = samplesales.rpd, DEFAULT;
Which instruct the BI Server to use read samplesales.rpd into memory as the default data model at startup.
- Cache file cache file is generated automatically by BI Server if the cache option is set to on, It is used to store query result from data source. When a query is submitted by user , BI Server will cache the query result and when a similar query is execute at later time. BI Server will return the result from the cache instead of resubmitting the query to backend data sources. Considering the fact that many of the query data is refresh on or twice a day, This feature will reduce workload to backend data source and improve query performance dramatically!