Defining database link by using Oracle Gateway

For configuring a remote non-Oracle database connections on Oracle gateway,
I followed below steps, hope this helps.

1) Create below file in the gateway, with appropriate values like the example below:
  Beware of the value of X in the file name: init<X>.ora
  X value will later be used in listener.ora file SID_NAME parameter.
  Beware of connect string line: HS_FDS_CONNECT_INFO=10.1.1.1:4100/mysydb1
  Ip,port and database name triple belongs to the remote sybase machine.

Server: Gateway
File name: /u01/app/oracle/product/11.1.0/dg4sybs/admin/initMYSYDB1.ora
  
# This is a sample agent init file that contains the HS parameters that are
# needed for the Transparent Gateway for Sybase
#HS_FDS_TRACE_LEVEL=OFF
HS_FDS_CONNECT_INFO=10.1.1.1:4100/mysydb1
HS_FDS_RECOVERY_ACCOUNT=RECOVER
HS_FDS_RECOVERY_PWD=RECOVER
HS_FDS_CONNECT_STRING="EnableSPColumnTypes=2"
HS_FDS_SUPPORT_STATISTICS=FALSE
HS_FDS_TRACE_LEVEL=DEBUG
HS_FDS_TRANSACTION_MODEL=COMMIT_CONFIRM
HS_FDS_TRACE_FILE_NAME = /tmp/dg4sybs_mysydb.trc
#
# Environment variables required for Sybase
#
set SYBASE=/u01/app/sybase
set LIBPATH=/u01/app/sybase/OCS-12_5/lib:/u01/app/sybase:/u01/app/oracle/product/11.1.0/lib
HS_FDS_QUOTE_IDENTIFIER=FALSE

 

2) In the gateway machine (in my example host ip: 10.1.1.200), Enter lines in listener.ora file:
Server: Gateway
File name: /u01/app/oracle/product/11.1.0/network/admin/listener.ora

MYSYDB_1522 =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS_LIST =
         (ADDRESS = (PROTOCOL = TCP)(HOST = 10.1.1.200) (PORT = 1522))
     )
   )
  )
SID_LIST_MYSYDB_1522 =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = MYSYDB1)
      (ORACLE_HOME = /u01/app/oracle/product/11.1.0)
      (PROGRAM = dg4sybs)
      (ENVS=LIBPATH=/u01/app/oracle/product/11.1.0/dg4sybs/driver/lib:/u01/app/oracle/product/11.1.0/lib)
    )
  )

3) Start the service by issueing below command:

lnsrctl start MYSYDB_1522

4) Enter TNS entry to Oracle server where you created dblink.
If it is RAC you must re-enter this information in all nodes.
10.1.1.200 ip belongs to gateway server.

Server: Local DB(s)
File name: /u01/app/product/DB/network/admin/tnsnames.ora

REMOTEDB =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = tcp)(HOST = 10.1.1.200)(PORT = 1522))
    (CONNECT_DATA =
      (SID = MYSYDB1)
    )
    (HS = OK)
  )
  
 
5) Create dblink in the database side, using the tns entry in previous step:

CREATE PUBLIC DATABASE LINK MYDBLINK
 CONNECT TO "user1"
 IDENTIFIED BY <PWD>
 USING 'REMOTEDB';
  
 
Troubleshooting :
1- 
 While testing with select * from dual@MYDBLINK;
 it was giving below error. This was because of a sybase side logon trigger.

 ORA-28500: connection from ORACLE to a non-Oracle system returned this message:
 [Oracle][ODBC Sybase Wire Protocol driver]Socket closed. {08S01}[Oracle][ODBC Sybase Wire Protocol driver]Sybase Network Connection has terminated. If a transaction was in progress it has been aborted. {08S01}[Oracle][ODBC Sybase Wire Protocol driver][Sybase ASE]Execution of login script '"sp_adm_check_int_users"' failed with last error = 11039. See server errorlog for details.
 {HY000,NativeErr = 1638}[Oracle][ODBC Sybase Wire Protocol driver]File not found '.odbc.ini'. {HY000,NativeErr = 1509}
 ORA-02063: preceding 3 lines from MYDBLINK

  
 sp_adm_check_int_users is a logon checking procedure, which authenticates conenctions according to source host ip/hostname.
 
 
2- You can check for any error logs in the following directory.
 
  /u01/app/oracle/product/11.1.0/dg4sybs/log
  
  -rw-r--r--    1 oracle   dba           11012 May 08 11:37 MYSYDB1_agt_65733070.trc
  -rw-r--r--    1 oracle   dba           11012 May 08 11:39 MYSYDB1_agt_59441834.trc
  -rw-r--r--    1 oracle   dba           11012 May 08 15:38 MYSYDB1_agt_54329962.trc
  -rw-r--r--    1 oracle   dba         2113496 May 09 19:05 MYSYDB1_agt_22414304.trc
  -rw-r--r--    1 oracle   dba           18585 May 10 15:46 MYSYDB1_agt_5701974.trc

3- You may get TNS error: ORA-12154: TNS:could not resolve the connect identifier specified
  In my case, it was I forgot to enter the tns entry in other node of the RAC.