Oracle Database "DEMO" could not be started while using DBUA (DBT-20010):

This is the issues generally facing while upgrading a database from 12C to 19C using DBUA.

Below is the error detail:

Symptoms: [FATAL] [DBT-20010] Specified database "demo" could not be started.

                  ACTION: Start the database manually and try again.

 Cause 1: The database entry in oratab file was not proper

Cat /etc/oratab or cat /var/opt/oratab

Demo: /u02/app/oracle/product/19.0.0:N

> ps -ef|grep pmon

ora_pmon_DEMO ==> the actual database was up and running as DEMO

 Solution: Ensure the database name and the oracle home value in oratab file is matching the actuals on the server.

 Cause 2:

ORACLE_HOME environment variable was not set properly

 Solution: Ensure that the all the Oracle related environment variables are pointing to target home before invoking dbua.

Cause 3:

Database was up and running from source home, but sqlplus binary was pointing to some other home on the server

ps -ef|grep pmon

 For My case Database was running on old home (i.e. in 12c)

This is can be confirm using sqlplus command.

Solution: Ensure that the sqlplus binary used to start the database is from the source Oracle home and not any other.

This can be done by verifying as follows :

> which sqlplus

/u02/app/oracle/product/19.0.0/bin/sqlplus

> echo $ORACLE_HOME

/u02/app/oracle/product/19.0.0

This issue also happens when an alias of sqlplus is present on the server. Though you might have set the Oracle Home properly, but sqlplus, because of alias will be picked up from some other home .

 Refer to Oracle Note :(Doc ID 2670689.1)

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