Oracle Tips

Oracle Database Name Resolution with OpenLDAP Anyone who has ever worked with the Oracle Database is most likely familiar with the tnsnames.ora file. The tnsnames.ora file is a text file that contains client side definitions for net service names, sometimes call aliases, needed to log in to an Oracle instance. This provides local name resolution by mapping net service names to connect description information for Oracle instances; similar to how the local hosts file for an operating system maps machine names to IP addresses. The tnsnames.ora file is commonly found in its default location under the ORACLE_HOME/network/admin directory.

One of the advantages of using a local tnsnames.ora file is that it is easy to create and edit entries. This is especially true when there are only a few entries to maintain and the file only needs to be distributed to a small number of Oracle client machines. The primary disadvantage of local naming is when there are a large number of client machines on the network, say 100 or even a 1000 clients, each required to have their own tnsnames.ora file. This problem gets compounded when frequent changes to the tnsnames.ora are required as a result of adding or moving database and the file has to be re-distributed to those clients.
A more efficient solution is to centralize the list of database names in a repository that every Oracle client can access. In the following article, I will demonstrate how to configure Oracle database naming in an LDAP directory. LDAP is for tnsnames.ora what DNS is for a local hosts file like /etc/hosts. Similar to how the local tnsnames.ora file works, when a client performs a lookup for a net server name in LDAP, it is given the appropriate connect descriptor information for the Oracle instance or service name.
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