Check DB Connection

From Local

From Remote

1. tnsping

• Oracle Client installation

NOTE: tnspin just check if the LISTENER service on the DB server is running

$> tnsping <TNS-Alias>
 or
$> tnsping <db-server-ip>:1521/<SID>

2. check_db_up.sql

• Oracle Client installation
• tnsnames.ora

whenever sqlerror exit 1;
connect username/password@<<TNS alias>>
select 1 from dual;
exit 0;

Run your bash like the follows

sqlplus /nolog @check_db_up.sq

If that returns 1, there was an error and the database isn't up.