To identify all instances associated with the Oracle home you want to remove, enter the following command, where dbname is the name of the database:

$ srvctl status database -d dbname

Alternately, you can check for registered instances by viewing the oratab file:

AIX, HP-UX, or Linux:

$ more /etc/oratab

Oracle Solaris:

$ more /var/opt/oracle/oratab

The output of this command contains entries similar to the following:

+ASM1:/u01/app/19.0.0/grid:N
CUST:/u01/app/oracle/product/19.0.0/dbhome_1:N

These entries show that the +ASM Oracle Automatic Storage Management instance in the Oracle Grid Infrastructure for a cluster home (/u01/app/19.0.0/grid) and the CUST Oracle database instance are associated with the Oracle home directory /u01/app/oracle/product/19.0.0/dbhome_1.