About Oracle Base Config

In a read-only ORACLE_HOME the configuration files reside in a location known as ORACLE_BASE_CONFIG.

Starting with Oracle Database 21c, the only available configuration is a read-only ORACLE_HOME where ORACLE_BASE_HOME and ORACLE_BASE_CONFIG are located separately from ORACLE_HOME.

In a read-only ORACLE_HOME, the ORACLE_BASE_CONFIG path is the same as ORACLE_BASE.

ORACLE_BASE_CONFIG/dbs contains the configuration files for ORACLE_HOME. Each file in the dbs directory contains $ORACLE_SID so that the directory can be shared by many different ORACLE_SIDs.

To print the ORACLE_BASE_CONFIG path, run the orabaseconfig command from the $ORACLE_HOME/bin directory:
$ setenv ORACLE_HOME /u01/app/oracle/product/21.0.0/dbhome_1
$ cd $ORACLE_HOME/bin
$ ./orabaseconfig

For example:

$ ./orabaseconfig
/u01/app/oracle

Where, /u01/app/oracle is ORACLE_BASE.