Using the file /data/oracle/product/11.2.0/db_1/dbs/initdb1.ora
Start with the command:
startup pfile='/data/oracle/product/11.2.0/db_1/dbs/initdb1.ora';
Startup error:
ORA-01506: missing or illegal database name
As shown in the image below:
The cause is that the initdb1.ora file is missing the db_name definition. Simply define one to fix it.
Startup succeeds on the next attempt.