have two databases, Oracle 8.1.7.4 on AIX
One of the database was assigned "tec" as its SID , and it had the following status of the service handler (Please note that

it has two duplicate service handler):
#lsnrctl status
LSNRCTL for IBM/AIX RISC System/6000: Version 8.1.7.4.0 - Production on 04-FEB-2004 16:29:21

Copyright 1998 Oracle Corporation. All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168. 56.29)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for IBM/AIX RISC System/6000: Version 8.1.7.4.0 - Production
Start Date 19-JAN-2004 22:08:34
Uptime 15 days 18 hr. 20 min. 47 sec
Trace Level off
Security OFF
SNMP ON
Listener Parameter File /oracle/app/oracle/product/8.1.7/network/admin/listener.ora
Listener Log File /oracle/app/oracle/product/8.1.7/network/log/listener.log
Services Summary...
tec has 1 service handler(s)
tec has 1 service handler(s)
The command completed successfully

And the other database was assigned "wjjs" as its SID, But it had only one service handler.
#lsnrctl status
LSNRCTL for IBM/AIX RISC System/6000: Version 8.1.7.4.0 - Production on 04-FEB-2004 16:27:17

Copyright 1998 Oracle Corporation. All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168. 56.22)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for IBM/AIX RISC System/6000: Version 8.1.7.4.0 - Production
Start Date 01-FEB-2004 00:56:12
Uptime 3 days 15 hr. 31 min. 4 sec
Trace Level off
Security OFF
SNMP OFF
Listener Parameter File /oracle/app/oracle/product/8.1.7/network/admin/listener.ora
Listener Log File /oracle/app/oracle/product/8.1.7/network/log/listener.log
Services Summary...
wjjs has 1 service handler(s)
The command completed successfully

Here I supply the listener.ora file of the two databases:
listener.ora of the "tec"
LISTENER =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.56.29)(PORT = 1521))
)

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = tec)
(ORACLE_HOME = /oracle/app/oracle/product/8.1.7)
(SID_NAME = tec)
)
)


listener.ora of the "wjjs"
LISTENER =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.56.29)(PORT = 1521))
)

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = wjjs2)
(ORACLE_HOME = /oracle/app/oracle/product/8.1.7)
(SID_NAME = wjjs2)
)
)