How to Modify Attributes That Replicate to the Global Catalog

The Global Catalog (GC) contains a partial replica of every object in the enterprise. This article discusses how to manipulate the attributes which make up the set values replicated to the GC. Deciding which attributes will replicate (in addition to the default attributes) requires careful planning with consideration for network traffic and necessary disk space.

Before describing how to set an attribute to replicate in the GC, it is important to note the effects this has on network replication traffic.

After an attributeSchema object is created, marking an additional attribute to replicate to the GC causes a full replication (also known as a "full sync") of all objects to the GC as described below. This behavior occurs on the versions of Windows 2000 listed in this article.

Every server has a full and write-able copy of its own domain. If that server is also a GC, the remaining domains in the forest are held as read-only, partial copies. "Partial" means that only a subset of the attributes is kept.

When an attribute is added to the GC, it is added to the partial copy subset (partial attribute set). This causes the GC to perform a "full sync" of all the read-only copies again to repopulate itself with only the partial attributes that it needs to hold. This full sync occurs even if the attribute property isMemberOfPartialAttributeSet is set to "True." Thus, it only does a full sync on the read-only partial copy domains and not its own write-able domain, the configuration directory partition or schema directory partition.

Notes:

"Directory partition" has been previous referred to as "naming context." Removals from the GC are handled locally without replication.

In order to modify the attributes that replicate to the Active Directory GC, you must modify the schema. To modify the schema, an administrator must be made a member of the "Schema Admins" group. In addition to being a member of this group, a registry key must be set on the Schema master. For additional information about this process, click the article number below to view the article in the Microsoft Knowledge Base: This article also describes steps that are performed in the Active Directory Schema Microsoft Management Console (MMC). You can acquire this snap-in through a full installation of the Windows 2000 Administration Tools or by registering Schmmgmt.dll in the system root on a Windows 2000 server.

To activate the Schema MMC snap-in follow these steps:

1. Click Start, click Run, type mmc, and then click OK.
2. On the MMC Console menu, click Add/Remove Snap-in....
3. Click Add, and then click Active Directory Schema.
4. Click Add, click Close, and then click OK.

You can also follow these steps to set the registry key discussed in the article mentioned above by way of the Schema MMC snap-in:

1. Highlight Active Directory Schema
2. Choose Action | Operations Master....
3. Click to select the box titled The Schema may be modified on this Domain Controller.
4. Click OK.

At this point, a Schema Administrator can add additional attributes to the GC. There are several methods to add additional attributes to the GC including the Schema MMC snap-in and ADSI scripts.

To Make Modifications Using Active Directory Schema MMC Snap-In

1. Click the Attributes folder in the snap-in.
2. In the right pane, scroll down to the desired attribute, right-click it, and then click Properties.
3. Click to select the Replicate this attribute to the Global Catalog check box.
4. Click OK.

If the above registry change is not made, the following error occurs when attempting to change the status of the replication to the GC:

To Make Modifications Using ADSI Scripts

Active Directory Services Interfaces (ADSI) can make modifications to the schema through its Lightweight Directory Access Protocol (LDAP) provider. The code below determines the location of the schema, bind to the attribute in the schema, and make the necessary changes to force it to replicate to the GC. If the above registry change is not made, the following error occurs when attempting to run the script:

For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base: For additional information about ADSI, see the following Microsoft Web site: