Expensive direct updates

If the data does not fit on the same page, Adaptive Server performs an expensive direct update, if possible. An expensive direct update deletes the data row, including all index entries, and then inserts the modified row and index entries.

Adaptive Server uses a table scan or an index to find the row in its original location and then deletes the row. If the table has a clustered index, Adaptive Server uses the index to determine the new location for the row; otherwise, Adaptive Server inserts the new row at the end of the heap.

An expensive direct updatemust meet these requirements:

An expensive direct update is the slowest type of direct update. The delete is performed on one data page, and the insert is performed on a different data page. All index entries must be updated, since the row location is changed.