Shrinking a database involves removing physical storage from it without losing the data in that storage.
Each partition in a database must be stored in a segment of the database. The partition is bound to the segment. When Adaptive Server moves data during an alter database ... off operation, it must move the data to other areas of the database where storage is permitted for this segment.
The alter database ... off operation fails if Adaptive Server cannot allocate space within the correct segment to receive a page being moved. Any data already moved remains in its new location.
Adaptive Server records all data movement in the log record.