This gives multiple instances of Oracle8 concurrent access to the same database. On some MPP platforms, such as IBM SP, disks are associated to nodes and a virtual shared disk software layer enables global access to all nodes. The Integrated Distributed Lock Manager coordinates modifications of data blocks, maintenance of cache consistency, recovery of failed nodes, transaction locks, dictionary locks, and SCN locks. Each CPU has full access to all shared memory through a common bus. Communication between nodes occurs via shared memory.
Performance is limited by the bandwidth of the memory bus.
Multiple SMP nodes can be used with Oracle Parallel Server in a tightly coupled system, where memory is shared among the multiple CPUs, and is accessible by all the CPUs through a memory bus. Examples of tightly coupled systems include the Pyramid, Sequent, and Sun SparcServer. It does not make sense to run Oracle Parallel Server on a single SMP machine, because the system would incur a great deal of unnecessary overhead from IDLM accesses. Performance is potentially limited in a tightly coupled system by a number of factors. This means that internal synchronization is faster than using the Lock Manager.