Unable to access DBCONN after upgrading to EHP7 in SAP system

You can test the connection using T-code: SE38 using ADBC_TEST_CONNECTION. You could check details of exception as below:

TRY.
EXEC SQL.
CONNECT TO 'ZUNIXDB_DBCON'
ENDEXEC.
EXEC SQL.
OPEN dbcur FOR
SELECT id FROM table
ENDEXEC.
CATCH cx_sy_native_sql_error INTO lr_cx_native_sql_error.