I was trying to use sqlplus
sqlplus /nologing
> connect internal as sysdba
ERROR:
ORA-24314:service handle not initialized
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sqlplus /nologing
> connect sys/change_on_install as sysdba
ERROR:
ORA-12560:service handle not initialized
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sqlplus /nologing
> connect internal/oracle as sysdba
ERROR:
ORA-01017:invalid username/password
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Thank you.