Update: 31 July 2015: In ABD SS6 this variable is predefined at the application level to be $(PROJ_DATASET)SETTING\ so no longer needs to be added to configurations as described in the article below, see Improving DataGroup System load time when using MicroStation tools for more information.
A little background: Microstation, AECOsim Building Designer's platform, stores data on elements using a system called EC data. AECOsim Building Designer (ABD) uses the DataGroup system. The two systems exist for reasons rooted in the development of Bentley's range of AEC tools. EC data does not curently support 100% of the DataGroup system's features so ABD is maintaining the DataGroup system until the two can be integrated completely in a future version of the software.
The result is that a conversion process is executed whenever you use a platform (i.e. MicroStation) tool that relies on EC data but needs to access data in the DG system. e.g. element selection, item browser. This process can cause delay in operation of affected tools. For instance, docking element selection will generally slow you down. (Note, the Building Element Info dialog accesses the DataGroup directly so does not experience this delay)
BB_DG_ECSCHEMA_CACHE is a new variable available in the SELECTseries 5 release. It specifies the path to a location where the DataGroup EC schema cache file can be stored.
Once set this cache is created and maintained in the specified location, typically named BuildingDataGroup.01.00.ecschema.xml.
This cache improves performance when accessing DataGroup content, in particular it minimises the delay in updating the Element Information dialog.
It will also speed up the load time for Thematic Maps.
The recommended location is in the project dataset so the active dataset specified by the PCF is always cached and variations in dataset content between projects are cached per project.
BB_DG_ECSCHEMA_CACHE = $(_USTN_PROJECTDATA)support/dataset/data/
to your PCF to store the cache file in the project dataset's data folder.
Even though the cache is stored at the network location that you assign, a local copy of the cache is created in the background, there is no need to direct this variable to a local folder to obtain the performance benefits.
Changes to the dataset, addition of custom parts for instance, are picked up automatically.
Do we need to set this variable for MicroStation, Navigator and View products too since it only exists in ABD?