Chapter 2. Planning the Directory Data14Data Format Size Owner Related toEmail address Text Many character IS department User's entryTable 2.3. Directory Data Characteristics2.3.4. Determining Level of ServiceThe level of service provided depends on the expectations of the people who rely on directory-enabledapplications. To determine the level of service each application expects, first determine how and whenthe application is used.As the directory evolves, it may need to support a wide variety of service levels, from production tomission critical. It can be difficult raising the level of service after the directory is deployed, so makesure the initial design can meet the future needs.For example, if the risk of total failure must be eliminated, use a multi-master configuration, whereseveral suppliers exist for the same data.2.3.5. Considering a Data MasterA data master is a server that is the master source of data. Any time the same information is storedin multiple locations, the data integrity can be degraded. A data master makes sure all informationstored in multiple locations is consistent and accurate. There are several scenarios that require a datamaster:• Replication among Directory Servers• Synchronization between Directory Server and Active Directory• Independent client applications which access the Directory Server dataConsider the master source of the data if there are applications that communicate indirectly with thedirectory. Keep the processes for changing data, and the places from which the data can be changed,as simple as possible. After deciding on a single site to master a piece of data, use the same site tomaster all of the other data contained there. A single site simplifies troubleshooting if the databaseslose synchronization across the enterprise.There are different ways to implement data mastering:• Master the data in both the directory and all applications that do not use the directory.Maintaining multiple data masters does not require custom scripts for moving data in and out of thedirectory and the other applications. However, if data changes in one place, someone has to changeit on all the other sites. Maintaining master data in the directory and all applications not using thedirectory can result in data being unsynchronized across the enterprise (which is what the directoryis supposed to prevent).• Master the data in some application other than the directory, and then write scripts, programs, orgateways to import that data into the directory.Mastering data in non-directory applications makes the most sense if there are one or twoapplications that are already used to master data, and the directory will be used only for lookups (forexample, for online corporate telephone books).
