The process of resolving a servicename (or database alias or global name) into a server'sphysical address is known as name resolution.While the information needed to perform name resolution betweenservice names and specific Oracle instances and hosts is normallymaintained in thetnsnames.ora file, that approach requires propagationof modifications to tnsnames.ora across theenterprise whenever there is a change to any component. This may beinconvenient or even impossible in installations where changes occuroften or where coordination of tnsnames.orafiles is difficult. To solve this problem, Oracle developed a productcalled Oracle Names, which provides dynamic resolution of servicenames through the use of an Oracle Names server. By using OracleNames, a network node only needs to know how to connect to the OracleNames server, which then resolves any service names without a needfor tnsnames.ora. In addition, Oracle Names isable to integrate with many native naming services, such as NetworkInformation Services (NIS), Novell NetWare Directory Services (NDS),and Banyan Vines StreetTalk.
The Oracle Names method for name resolution has a number of positiveattributes. This method:
Resolves service names quickly
Allows central control of service names and corresponding physical attributes (e.g., hosts and instance names)
Provides dynamic access to modified locations
Provides fault tolerance by supporting multiple name servers
In order to use Oracle Names, one or more Names servers must beconfigured and implemented using the Oracle Network Manager,described later in this chapter. Once installed, Names servers areserver-based services and must be controlled using the programnamesctl. This control program, which is similarto the lsnrctl control program for the SQL*Netlistener, performs routine tasks such as starting and stopping theNames server, obtaining status information, and maintaining the namecache.
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