Red Hat DIRECTORY SERVER 7.1 - DEPLOYMENT Deployment Manual page 36

Performing a Site Survey
Here are some ways you can 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 the directory and the other applications. However,
if data changes in one place, someone has to change it on all the other sites.
Maintaining master data in the directory and all applications not using the
directory can result in data being unsynchronized across your enterprise
(which is what your directory is supposed to prevent).
• Master the data in some application other than the directory, and then write
scripts, programs, or gateways to import that data into the directory.
Mastering data in non-directory applications makes the most sense if you can
identify one or two applications that you already use to master your data, and
you want to use your directory only for lookups (for example, for online
corporate telephone books).
How you maintain master copies of your data depends on your specific needs.
However, regardless of how you maintain data masters, keep it simple and
consistent. For example, you should not attempt to master data in multiple sites,
then automatically exchange data between competing applications. Doing so
leads to a "last change wins" scenario and increases your administrative
overhead.
For example, suppose you want to manage an employee's home telephone
number. Both the LDAP directory and a human resources database store this
information.The human resources application is LDAP enabled, so you can write
an automatic application that transfers data from the LDAP directory to the
human resources database, and vice versa. However, if you attempt to master
changes to that employee's telephone number in both the LDAP directory and the
human resources data, then the last place where the telephone number was
changed overwrites the information in the other database. This is acceptable as
long as the last application to write the data had the correct information. But if
that information was old or out of date (perhaps because, for example, the human
resources data was reloaded from a backup), then the correct telephone number
in the LDAP directory will be deleted.
36 Red Hat Directory Server Deployment Guide • May 2005