HP OpenVMS Alpha Version 8.3 and HP OpenVMS Version
•Shared page tables
•Expandable global page table
•Reserved memory registry
DECdtm Services
The DECdtm services embedded in the OpenVMS op- erating system support fully distributed databases us- ing a
DECdtm services allow applications to define global transactions that can include calls to any number of HP data management products. Regardless of the mix of data management products used, the global transac- tion either commits or aborts. OpenVMS is unique in providing transaction processing functionality with base operating system services.
DECdtm features include:
•Embedded OpenVMS system services that support the DECtp architecture, providing the features and technology for distributed transaction processing.
•Ability for multiple disjoint resources to be updated automatically. These resources can be either physi- cally disjointed on different clusters at separate sites, or logically disjointed in different databases on the same node.
•Ability to use the X/Open Distributed Transaction Processing XA interface that enables the DECdtm transaction manager to coordinate
•Robust application development. Applications can be written to ensure that data is never in an incon- sistent state, even in the event of system failures.
•Ability to be called using any HP TP monitor or database product. This is useful for applications us- ing several HP database products.
Interprocess Communication
OpenVMS provides the following facilities for applica- tions that consist of multiple cooperating processes:
•Mailboxes as virtual devices that allow processes to communicate with queued messages.
•Shared memory sections on a single processor or an SMP system that permit multiple processes to access shared address space concurrently.
•Galaxywide sections on a Galaxy platform that permit multiple processes in multiple instances to access shared address space concurrently.
•Common event flags that provide simple synchro- nization.
•A lock manager that provides a more comprehen- sive enqueue/dequeue facility with multilevel locks, values, and asynchronous system traps (ASTs).
•Intracluster communication services through which two processes running on the same system or on dif- ferent OpenVMS Cluster nodes can establish a con- nection and exchange data.
•Logical names through which one process can pass information to other processes running on the same system or on different OpenVMS Cluster nodes.
•Network interprocess communication is available via TCP/IP Services and
Symmetric Multiprocessing (SMP)
OpenVMS provides symmetric multiprocessing (SMP) support for Alpha and Integrity servers multiprocessor systems. SMP is a form of tightly coupled multipro- cessing in which all processors perform operations si- multaneously. All processors perform operations in all OpenVMS access modes, user, supervisor, executive, and kernel.
OpenVMS SMP configurations consist of multiple CPUs executing code from a single shared memory address space. Users and processes share a single copy of OpenVMS for Integrity servers or OpenVMS Alpha ad- dress space. SMP also provides simultaneous shared access to common data in global sections to all proces- sors. OpenVMS SMP selects the CPU where a process will run based on its priority and in special cases as di- rected by the application. OpenVMS uses a specialized scheduling algorithm when running a nonuniform mem- ory access (NUMA) platform.
SMP support is an integral part of OpenVMS and is provided to the user transparently. Because an SMP system is a single system entity, it is configured into a network and OpenVMS Cluster configurations as a single node.
The maximum number of supported CPUs in an SMP configuration is 32.
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