Handling processor-intensive operations in a data processing system

Provided are a system and a method for data retrieval which identify from requested data retrieval operations those operations which require a particular processing task to be performed, and then separate those operations from operations not requiring the processing task. The separated sets of tasks are queued separately for independent processing. This enables resource scheduling to be performed which avoids the operations which do not require performance of the task from having to wait for the operations which do require the task. This is an advantage where the task is a processor-intensive task such as digital watermarking of images.A particular resource allocation method includes enqueuing the set of operations requiring the processing task in a circularly linked list and then employing a scheduler to implement a round-robin allocation of resources for each of the system users in turn.Also provided is a pre-fetch policy whereby sets of data objects are retrieved from a data repository for processing in response to data retrieval requests and post-retrieval processing such as watermarking is initiated before an individual data object in the set has been selected.