When you install your first domain controller, a large number of attributes are installed in the schema. Some of these are used in the Active Directory and in the Global Catalog:

Name Syntax Description
alt-Security-Identities Unicode String Alt-Security-Identities
common-Name Unicode String Common-Name
display-Name Unicode String Display-Name
given-Name Unicode String Given-Name
group-Type Integer Group-Type
keywords Unicode String Keywords
l Unicode String Locality-Name
lDAP-Display-Name Unicode String LDAP-Display-Name
legacy-Exchange-DN Unicode String Legacy-Exchange-DN
location Unicode String Location
mail Unicode String E-mail-Addresses
mSMQ-Digests Octet String MSMQ-Digests
mSMQ-Label Case Insensitive String MSMQ-Label
mSMQ-Owner-ID Octet String MSMQ-Owner-ID
mSMQ-Queue-Type Octet String MSMQ-Queue-Type
mS-SQL-Alias Unicode string MS-SQL-Alias
mS-SQL-Database Unicode string MS-SQL-Database
mS-SQL-Name Unicode string MS-SQL-Name
mS-SQL-Version Unicode string MS-SQL-Version
name Unicode string RDN
netboot-GUID Octet string Netboot-GUID
object-Category Distinguished Name Object-Category
object-Guid Octet string Object-Guid
object-Sid SID Object-Sid
organizational-Unit-Name Unicode string Organizational-Unit-Name
primary-Group-ID Integer Primary-Group-ID
sAM-Account-Name Unicode string SAM-Account-Name
sAM-Account-Type Integer SAM-Account-Type
service-Principal-Name Unicode string Service-Principal-Name
sID-History SID SID-History
surname Unicode string Surname
uNC-Name Unicode string UNC-Name
user-Account-Control Integer User-Account-Control
user-Principal-Name Unicode string User-Principal-Name
uSN-Changed Larger Integer USN-Changed
uSN-Created Larger Integer USN-Created

NOTE: The above attributes have the Index this attribute in the Active Directory and Replicate this attribute to the Global Catalog options enabled.

You can use the Active Directory Schema snap-in in the MMC to modify the schema, but you must first implement tip 2645.

NOTE: Microsoft recommends careful consideration and planning prior to modifying the schema.

The following attributes also have their flags set for Ambiguous Name Resolution (ANR):

Display-Name
Given-Name
Legacy-Exchange-DN
RDN
SAM-Account-Name
Surname