What is the Global Catalog?
The Global Catalog (GC) contains an entry for every object in an enterprise
forest but only a few properties for each object. An entire forest shares a GC,
with multiple servers holding copies. You can perform an enterprisewide forest
search only on the properties in the GC, whereas you can search for any property
in a userís domain tree. Only Directory Services (DSs) or domain controllers
(DCs) can hold a copy of the GC.
Configuring an excessive number of GCs in a domain wastes network bandwidth
during replication. One GC server per domain in each physical location is
sufficient. Windows NT sets servers as GCs as necessary, so you donít need to
configure additional GCs unless you notice slow query response times.
Because full searches involve querying the whole domain tree rather than the
GC, grouping the enterprise into one tree will improve your searches. Thus, you
can search for items not in the GC.
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