Querying for Category 1 or 2 Schema Objects
The systemFlags attribute of attributeSchema and classSchema objects is an integer bitmask that contains flags that indicate additional system qualities of the attribute or class. The ADS_SYSTEMFLAG_ENUM enumeration contains values that correspond to the bits you can set in the systemFlags attribute. There are additional systemFlags bits that you cannot set, such as the 0x10 bit which indicates whether the attribute or class is category 1 or category 2. The 0x10 bit is set for category 1 objects, which are the classes and attributes included in the base schema included with the system. The bit is not set for category 2 attributes and classes, which are extensions to the schema. If no systemFlags property exists on an attributeSchema or classSchema object, it is category 2.
The LDAP_MATCHING_RULE_BIT_AND matching rule can be used to search for objects that have the 0x10 flag set in the systemFlags attribute. For more information, see Search Filter Syntax.
Querying for Category 1
The following query string searches for category 1 attributes (attributeSchema objects with the 0x10 bit set in the systemFlags property).
Be aware that, in the example above, the LDAP query syntax requires decimal values; therefore, the hex value of the flag must be converted to decimal. In this case, category 1 bit is 0x10 so the filter value must be specified as 16.
Querying for Category 2
The following query string searches for category 2 attributes (attributeSchema objects that do not have the 0x10 bit set in the systemFlags property).
Be aware that this query also returns attributeSchema objects that do not have a systemFlags property, and, therefore, implicitly do not have the specified flag set.