NOTE:

Any descendant container entries need to be created separately on the Windows server by an administrator; Windows Sync does not create container entries.

7.1.2 Changelogs

The Directory Server maintains a changelog, a database that records modifications that have occurred. The changelog is used by Windows Sync to coordinate and send changes made to the Windows synchronization peer server. Changes to entries in the Windows server are found by using Active Directory's Dirsync search feature. Because there is no changelog on the Active Directory side, the Dirsync search is issued, by default, periodically every five minutes. Using Dirsync ensures that only those entries that have changed since the previous search are retrieved.

7.1.3 Controlling synchronization

Windows Sync provides some control over which entries are synchronized to give sufficient flexibility to support different deployment scenarios. This control is set through different configuration attributes set in the Directory Server:

•Within the Windows subtree, only entries with user or group object classes can be synchronized to Directory Server. When creating the synchronization agreement, there is an option to synchronize new Windows user and group entries as they are created. If these attributes are set to on, then existing Windows entries are synchronized to the Directory Server, and entries as they are created in the Windows server are synchronized to the Directory Server.

• On the Directory Server, only entries with the ntUser or ntGroup object classes and required attributes can be synchronized.

Directory Server passwords are synchronized along with other entry attributes because plaintext passwords are retained in the Directory Server changelog. The Password Sync Service is needed to catch password changes made on the Windows server. Without the Password Sync Service, it would be impossible to have Windows passwords synchronized because passwords are hashed in the Windows server, and the Windows hashing function is incompatible with the one used by Directory Server.

7.2 Planning windows synchronization

It may be useful to assess the type of information, Windows servers, and other considerations before setting up synchronization, similar to the site surveys for organizing data or planning replication.

7.2.1 Resource requirements

Synchronization uses server resources. Consider the following resource requirements when defining the replication strategy:

•Disk usage — The changelog is written after each update operation. Servers receiving many update operations may see higher disk usage. In addition, a single changelog is maintained for all replication databases and synchronized databases. If a supplier contains multiple replicated and synchronized databases, the changelog is used more frequently, and the disk usage is even higher.

•Server threads — The synchronization agreement uses one server thread.

•File descriptors — The number of file descriptors available to the server is reduced by the changelog (one file descriptor) and each replication and synchronization agreement (one file descriptor per agreement).

94 Designing synchronization