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Setup Oracle Database Link to MySQL

This Blog describes how to set up a Database link from an Oracle Database to a MySQL Database. As an example serves an Oracle Standard Edition Two Version 19c (19.14.0) Database with the Standard Edition High Availability (SEHA) configuration on Oracle Linux 8.

Packageinstallation

For the installation two RPM-Packages are needed:

• yum install unixODBC
• Download mysql-connector-odbc-8.0.28-1.el8.x86_64.rpm
• rpm -ihv mysql-connector-odbc-8.0.28-1.el8.x86_64.rpm

The package unixODBC installs the basic libraries including /usr/lib64/libodbc.so which is needed later and the files /etc/odbc.ini as well as /etc/odbcinst.ini. Furthermore the tool /usr/bin/isql belongs to that package

The package mysql-connector-odbc then installs the specific mysql libraries. The file /etc/odbcinst.ini is also going to be adjusted

ODBC Configuration

For the next step the ODBC client will be configured. For this, the configuration for one or more connections is entered in /etc/odbc.ini.  

Example:

[TESTMYDB]
Description     = Test-MYSQL-Datenbank
Driver          = /usr/lib64/libmyodbc8w.so
Trace           = no
Server          = 192.168.168.168
Port            = 3306
Database        = daten
User            = TESTUSER
Password        = passwort

It is important to have the name of the entry (TESTMYDB) and the correct driver. The driver for a unicode MySQL Database is libmyodbc8w.so. Otherwise  libmyodbc8a.so can be used for a MySQL Database with a 1-Byte character set.

With this it should be possible to connect to the MySQL database from the server.

isql TESTMYDB TESTUSER passwort

Gateway Installation

For the next step, the Oracle Gateway software will be installed. Unfortunately it is still necessary to unpack the software first and then install it:

cd /u05/share/software
unzip LINUX.X64:193000_gateways.zip
cd gateways
./runInstaller

In the example the gateway for MS-SQL is also installed. This is not important for this configuration.

Thus the gateway is installed in the directory /u01/app/oracle/product/19c/gwhome_1.

Gateway Configuration

Three components are responsible for the configuration:

• listener.ora
• tnsnames.ora
• init<GATEWAYNAME>.ora

listener.ora

LISTENER=
   (DESCRIPTION=
      (ADDRESS_LIST=
         (ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER))
         (ADDRESS=(PROTOCOL=TCP)(HOST=seha01)(PORT=1521))
      )
   )

SID_LIST_LISTENER =
   (SID_LIST=
      (SID_DESC=
         (SID_NAME=TESTMYDB)
         (ORACLE_HOME=/u01/app/oracle/product/19/gwhome_1)
         (PROGRAM=dg4odbc)
      )
   )

The SID_NAME must correspond to the name in the /etc/odbc.ini file. Of course there can be further SIDs for databases or further ODBC connections. On the second SEHA server the parameter “HOST” must be adjusted.

tnsnames.ora

TESTMYDB =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = seha01)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = seha02)(PORT = 1521))
    (CONNECT_DATA =
      (SID = TESTMYDB)
    )
    (HS = OK)
  )

For RAC or SEHA databases, the scan address cannot be used here. Instead, the HOSTS has to be specified explicitly.

The TNS alias may have a different name than the SID, which again must be identical to the entry in /etc/odbc.ini.

initTESTWEBDB.ora

HS_FDS_CONNECT_INFO = TESTWEBDB
#HS_FDS_TRACE_LEVEL = OFF
#HS_LANGUAGE = AMERICAN_AMERICA.WE8ISO8859P15
HS_FDS_SHAREABLE_NAME = /usr/lib64/libodbc.so

The name of the file must correspond to the name of the odbc.ini entry.
It is important that the parameter HS_FDS_SHAREABLE_NAME is not the ODBC library of MySQL but the so called “ODBC Drive Manager“. In this case it is the libodbc.so from the unixODBC package.

Database-Link

After all the preparation, the database link can now be created as usual:

CREATE DATABASE LINK jostest
CONNECT TO "TESTUSER" IDENTIFIED BY "password"
USING 'TESTMYWEBDB";

With this the connection to the MySQL database should work.
If the following error occurs:

ORA-28500: connection from ORACLE to a non-Oracle system returned this message:
[

This is probably because the MySQL database is not a Unicode database. The easiest way to solve the problem is to set the following parameter in the initTESTMYDB.ora file:

HS_LANGUAGE = AMERICAN_AMERICA.WE8ISO8859P15

When accessing the MySQL databases, please note that tables and databases are usually written in lower case. So it is better to put the database and table names in double quotation marks.

SELECT * FROM "daten"."test"@jostest;

That’s it.

If something is still missing or errors occurred, then please send a short message to me or leave a comment on the blog.

Good luck!