ASA Programming Guide
Using SQL in Applications
Introduction to cursors
You do not need to use cursors in database applications, but they do provide a number of benefits. These benefits follow from the fact that if you do not use a cursor, the entire result set must be transferred to the client for processing and display:
Client-side memory For large results, holding the entire result set on the client can lead to demanding memory requirements.
Response time Cursors can provide the first few rows before the whole result set is assembled. If you do not use cursors, the entire result set must be delivered before any rows are displayed by your application.
Concurrency control If you make updates to your data and do not use cursors in your application, you must send separate SQL statements to the database server to apply the changes. This raises the possibility of concurrency problems if the result set has changed since it was queried by the client. In turn, this raises the possibility of lost updates.
Cursors act as pointers to the underlying data, and so impose proper concurrency constraints on any changes you make.