Try This entry in your listener.ora:

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME= ORCL)
(ORACLE_HOME= /opt/app/oracle/product/7.3.4)
(SID_NAME = ORCL)
)
(SID_DESC =
(GLOBAL_DBNAME= ORAL)
(ORACLE_HOME= /opt/app/oracle/product/7.3.4)
(SID_NAME = ORAL)
)
)

Don't forget to include relevant entries in your tnsnames.