The sysusages table in the master database keeps track of all of the space that you assign to all Adaptive Server databases.
create database and alter database allocate new space to the database by adding a row to sysusages for each database device or device fragment. When you allocate only a portion of the space on a device with create or alter database, that portion is called a fragment.
The system procedures sp_addsegment, sp_dropsegment, and sp_extendsegment change the segmap column in sysusages for the device that is mapped or unmapped to a segment. Chapter 23, “Creating and Using Segments,” discusses these procedures in detail.
