ORACLE error while dbstart command
I have faced the similar issue. The reason, why it has happened was the invalid entry in the /etc/oratab.

As dbstart script suggests, to configure, update /etc/oratab with instances that need to be started up. The entries are of the form:

$ORACLE_SID:$ORACLE_HOME:&lt;N|Y|W&gt;:


An example entry:

main:/usr/lib/oracle/emagent_10g:Y