| Show Traditional virtual memory techniques provide some potential solutions to the problem of virtual database modifications. Two of these techniques are write back and write through. The write-back technique causes dirty pages of data to be written back to the underlying storage at the time they are to be replaced by the page replacement algorithm. The write-through technique causes modified pages to be written to the underlying storage at the time the modifications are made. The adaptation of these techniques for management of dirty pages in a virtual database system must be evaluated. Another area of work that is required is the enhancement of exception handling in the virtual database system. A virtual database system has at least two additional areas of potential exceptions that may not be a part of the standard database system: the network and the physical database system. The correct handling of exceptions is vital to the successful application of virtual database technology. The difficulty of handling exceptions properly is compounded if database modifications are allowed in the virtual database system. Improper handling of an exception in conjunction with database modifications could result in the loss of information in the database. A third area of future work is the optimization of a virtual database. The techniques employed by the virtual-database prototype aim to reduce the mean latency caused by the transfer of data from the physical database. Work is still required to refine this type of optimization. It should also be possible to reduce the mean latency associated with the processing of a message by the VAM process. The reduction in latency could be accomplished by enabling the database-access primitives to send a 75 |
