Overview#Schema Partition generally holds the schema
Schema Partition Microsoft Active Directory#Schema Partition that contains the classSchema and attributeSchema objects that define the types of ObjectClasses that can exist in the Microsoft Active Directory forest. All Domain Controllers in an AD Forest has a replica of the same Schema Partition. All modifications to the Schema Partition is performed by the Schema Master FSMO Role
This information is synchronized between servers, using a process called Schema Skulk or Schema Sync, and it means that each server has a complete copy of the schema.
The Schema Sync process starts with the server that contains the Master Replica of the Partition Root Entry and propagates to the other servers with a copy of Partition Root Entry. Then it continues with the servers in the child partitions, until all servers have received a copy of the schema.
The Partition ID of the Schema partition is always 1.