There are three key top-level directories in Oracle Business Intelligence 12c.
ORACLE_HOME - for binaries.
There is one ORACLE_HOME for each host, or mounted from shared storage.
DOMAIN_HOME - for configuration, and logs.
There is one DOMAIN_HOME for each host (also referred to as BI_DOMAIN, or bidomain).
SDD (Singleton Data Directory) - for metadata and other cross-cluster files.
There is one SDD for each domain.
The SDD path (by default DOMAIN_HOME/bidata) is defined in the file bi-environment.xml, located in:
DOMAIN_HOME/config/fmwconfig/bienv/core/bi-environment.xml
Note:
If you have just created a domain on one host, then SDD is set to DOMAIN_HOME/bidata.
If you have scaled-out, the SDD changes to use mounted shared storage. In this case, the SDD will not be DOMAIN_HOME/bidata.