When you install Replication Server, you set up a disk partition that Replication Server uses to establish stable queues. During replication operations, Replication Server temporarily stores updates in these queues.
Inbound queue – holds messages only from a Replication Agent. If the database you add contains primary data, or if request stored procedures are to be executed in the database for asynchronous delivery, Replication Server creates an inbound queue and prepares to accept messages from a Replication Agent for the database.
Subscription materialization queue – holds messages related to newly created or dropped subscriptions. This queue stores a valid transactional “snapshot” from the primary database during subscription materialization or from a replicate database during dematerialization.
You can add more partitions later if your replication system requires more space for stable queues.
See the Replication Server Troubleshooting Guide for information on how to examine queue contents for troubleshooting purposes.