Linking to SQL Server from Oracle 10g on 64bit Linux

Question

I have this working, so I thought I would post my steps.
In versions 8 to 10 of Oracle, the software for making these connections was known as Heterogeneous Services. It was 32bit only software and the actual binary file that was executed when querying a non oracle database was $ORACLE_HOME/bin/hsodbc. When a query was made to the linked database, a process was started on the machine with the name of hsodbcXXX (where XXX is the name of the DSN).
In version 11g of Oracle this software is now referred to as Database Gateways and there is a 64bit version as well as a 32bit version. The binary file that is executed in this case is $ORACLE_HOME/bin/dg4odbc.
Fortunately the 64bit Database Gateway software can also be used with Oracle 10g databases as long as it is up to version 10.2.03 and has the odbc compatibility patch installed. (5965763).
To make use of this, we need to install the 11g ODBC Gateway into a separate ORACLE_HOME and start a listener from that environment. We can then make use of that listener from the 10g environment.
So here is what I did to get this working: (Note: DSN = MyDSN)
1.     Download and install 64bit ODBC driver with support for 64-bit ULEN from Easysoft. The file is named odbc-sqlserver-1.1.4-linux-x86-64-ul64.tar. You'll need to email Easysoft support for the URL. Create the DSN entry as part of the install. At the end of the process it can test the DSN. The query should come back with info about the SQL Server. Test the connection using isql from the /opt/easysoft/unixODBC/bin directory to verify that it works as well (/opt/easysoft/unixODBC/bin/isql –v MyDSN). Note, I installed easysoft driver under /opt rather than the /usr/local which is the default. /usr/local/easysoft is a symlink to /opt/easysoft.
2.     Install ODBC gateway via the 11g Gateways installer. You can do a custom install and deselect all but the ODBC Gateway component. (http://download.oracle.com/otn/linux/oracle11g/linux.x64_11gR1_gateways.zip)
3.     Create a /home/oracle/11g_environment.sh script that sets 11g ORACLE_HOME, PATH, and LD_LIBRARY_PATH variables. It should look something like this:
#set ORACLE ENV vars for 11g
ORACLE_HOME=/u01/app/oracle/product/11.1.0/tg_1 # (assuming that is where ODBC Gateway was installed)
PATH=/bin:/usr/bin:/u01/app/oracle/product/11.1.0/tg_1/bin:/opt/easysoft/bin:/opt/easysoft/unixODBC/bin
LD_LIBRARY_PATH=/opt/easysoft/lib:/opt/easysoft/unixODBC/lib:/u01/app/oracle/product/11.1.0/tg_1/lib
export ORACLE_HOME
export PATH
export LD_LIBRARY_PATH
4.     Create $ORACLE_HOME/hs/admin/initMyDSN.ora, $ORACLE_HOME/network/admin/listener.ora, and $ORACLE_HOME/network/admin/tnsnames.ora under 11g structure. They are as follows:
initMyDSN.ora:
# This is a sample agent init file that contains the HS parameters that are
# needed for an ODBC Agent.
# HS init parameters
HS_FDS_CONNECT_INFO=MyDSN
HS_FDS_TRACE_LEVEL=0
HS_FDS_TRACE_FILE_NAME=MyDSN.trc
HS_FDS_SHAREABLE_NAME=/opt/easysoft/unixODBC/lib/libodbc.so
HS_FDS_SUPPORT_STATISTICS=FALSE
# ODBC specific environment variables
#set ODBCINI=/etc/odbc.ini
#set ODBCINSTINI=/etc/odbcinst.ini
#set LD_LIBRARY_PATH=/opt/easysoft/lib:/opt/easysoft/unixODBC/lib:/u01/app/oracle/product/11.1.0/lib
#set PATH=$PATH:/opt/easysoft/unixODBC/bin:/opt/easysoft/bin/
# Environment variables required for the non-Oracle system
#set <envvar>=<value>
listener.ora
MyDSN =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1522))
SID_LIST_MyDSN =
(SID_LIST =
(SID_DESC=
(SID_NAME=MyDSN)
(ORACLE_HOME = /u01/app/oracle/product/11.1.0/tg_1)
(PROGRAM=dg4odbc)
(ENVS=LD_LIBRARY_PATH=/opt/easysoft/lib:/opt/easysoft/unixODBC/lib:/u01/app/oracle/product/11.1.0/tg_1/lib)
tnsnames.ora
# tnsnames.ora Network Configuration File:
# Generated by Oracle configuration tools.
EXTPROC_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
MyDSN =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST=localhost)(PORT=1522))
(CONNECT_DATA=(SID=MyDSN))
(HS=OK)
5.     Add another entry for MyDSN in /u01/app/oracle/product/10.2.0/db_1/network/admin/tnsnames.ora so tnsping works in 10g environment as well.
MyDSN =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST=localhost)(PORT=1522))
(CONNECT_DATA=(SID=MyDSN))
(HS=OK)
*** Notice that the MyDSN listener runs on a different port (1522) as it is a separate listener.
6.     Login to machine as user oracle and source the 11g environment script. “source ~/11g_environment.sh”. Now start the listener. “cd $ORACLE_HOME/bin”. “./lsnrctl start MyDSN”.
7.     Login to a new shell as user oracle with a 10g environment.
8.     Run sqlplus and create the database link. “CREATE PUBLIC DATABASE LINK SQLSERVER connect to “<someuser>” IDENTIFIED BY “<somepass>” USING ‘MyDSN’;”
9.     test the link. “select * from information_schema.tables@SQLSERVER;”
If it is successfull, you should see a system process named "dg4odbcMyDSN".

Answer 1

So what have you found out for yourself so far (considering the solution to this is easily found on the web)?
Have you looked up Heterogeneous Services?