When you insert or delete data, and when you synchronize join indexes, Sybase IQ needs some working space in the IQstore. This space is reclaimed for other purposes when the transaction that needs it commits.
Ordinarily, as long as you maintain a reasonable percentage of free space in your IQ store, you will have enough free space. However, for certain deletions, depending on the size of the data and its distribution among database pages, you may need a large amount of working space. In the case where you are deleting a major portion of your database, and the data is distributed sparsely across many pages, you could temporarily double the size of your database.