OCA /OCP Oracle Database 11g A ll-in-One Exam Guide- P8:There is an ever increasing demand for staff with IT industry certification. The benefits to employers are significant—they can be certain that staff have a certain level of competence—and the benefits to the individuals, in terms of demand for their services, are equally great. Many employers are now requiring technical staff to have certifications, and many IT purchasers will not buy from firms that do not have certified staff. | OCA OCP Oracle Database 11g All-in-One Exam Guide 26 TIP Determining the optimal size is a matter for performance tuning but it is probably safe to say that most databases will need a shared pool of several hundred megabytes. Some applications will need more than a gigabyte and very few will perform adequately with less than a hundred megabytes. The shared pool is allocated at instance startup time. Prior to release 9i of the database it was not possible to resize the shared pool subsequently without restarting the database instance but from 9i onward it can be resized up or down at any time. This resizing can be either manual or from release 10g onward automatic according to workload if the automatic mechanism has been enabled. EXAM TIP The shared pool size is dynamic and can be automatically managed. The Large Pool The large pool is an optional area that if created will be used automatically by various processes that would otherwise take memory from the shared pool. One major use of the large pool is by shared server processes described in Chapter 4 in the section Use the Oracle Shared Server Architecture. Parallel execution servers will also use the large pool if there is one. In the absence of a large pool these processes will use memory on the shared pool. This can cause contention for the shared pool which may have negative results. If shared servers or parallel servers are being used a large pool should always be created. Some I O processes may also make use of the large pool such as the processes used by the Recovery Manager when it is backing up to a tape device. Sizing the large pool is not a matter for performance. If a process needs the large pool of memory it will fail with an error if that memory is not available. Allocating more memory than is needed will not make statements run faster. Furthermore if a large pool exists it will be used it is not possible for a statement to start off by using the large pool and then revert to the shared pool if the .
