emca fails with "Database instance is unavailable" though available
By Giri Mandalika-Oracle on Nov 23, 2012
The following example shows the symptoms of failure, and the exact error message.
$ emca -repos create ... Password for SYSMAN user: Do you wish to continue? [yes(Y)/no(N)]: Y Nov 19, 2012 10:33:42 AM oracle.sysman.emcp.DatabaseChecks \ checkDbAvailabilityImpl WARNING: ORA-01034: ORACLE not available Nov 19, 2012 10:33:42 AM oracle.sysman.emcp.DatabaseChecks \ throwDBUnavailableException SEVERE: Database instance is unavailable. Fix the ORA error thrown and run EM Configuration Assistant again. Some of the possible reasons may be : 1) Database may not be up. 2) Database is started setting environment variable ORACLE_HOME with trailing '/'. Reset ORACLE_HOME and bounce the database. For eg. Database is started setting environment variable ORACLE_HOME=/scratch/db/ . Reset ORACLE_HOME=/scratch/db and bounce the database.
Ensure that the ORACLE_HOME is pointing to the right location in $ORACLE_HOME/bin/emca file.
Rather than installing from scratch, if ORACLE_HOME was copied over from another location, likely it results in wrong location for ORACLE_HOME in several Enterprise Manager (EM) specific scripts and files. It usually happens when the directory structure on the target machine is not identical to the structure on the original/source machine, including the top level directory location where Oracle RDBMS was installed properly using the installer.