gtpc3m0nConcepts and Structures

TPF System Coupling Facility Support

Coupling facility (CF) support provides data sharing capabilities that allow TPF routines, subsystems, system products, and applications running in a processor configuration to use a CF for high-availability data sharing. A CF is an IBM processor (sometimes referred to as a central processing complex (CPC)) that is used to centralize storage for all attached processors in a processor configuration by providing shared storage and shared storage management functions. CF support provides connectivity to a CF for use by TPF system functions.

You can add one or more CFs from a TPF processor to the processor configuration. Applications can connect to CF list or cache structures on CFs that have been added to the processor configuration. A CF list structure is a named piece of storage on a CF that enables users to share information organized as entries on a set of lists or queues. A CF cache structure is a named piece of storage on the CF that enables users to share information and allows high-performance sharing of frequently referenced data. A user refers to an application or an instance of an application using connection services to access a CF structure.The first connect request issued to a particular CF structure causes that structure to be allocated before establishing the connection.

An application that connects to a CF list structure can monitor individual lists to determine when list entries have been created on that list. When a list changes from empty state to nonempty state (that is, when a list entry is added to a previously empty list), an application-defined exit is called. This eliminates the need for application polling of lists and simplifies programming requirements.

An application that connects to a CF cache structure can automatically notify affected users when shared data in the cache is changed. The application can also determine whether the local copy of shared data is valid by checking system-maintained validity indicators. See TPF Database Reference for more information about CF cache structures.

When an application no longer requires access to a CF structure, the application can disconnect from the CF structure. Depending on the parameters specified when the CF structure was allocated, a disconnect by the last connector to a CF structure either causes deallocation of the CF structure or allows it to remain allocated for subsequent connections to occur.

A CF may be added to multiple processor configurations in a TPF multiprocessor complex. A CF that has been added to a TPF processor configuration may not be shared with any other processor that is not in the TPF multiprocessor complex even if that other processor is also running the TPF system.

Coupling Facility Record Lock Support

The limited lock facility (LLF) and the concurrency filter lock facility (CFLF), which are two external lock facilities (XLFs) supported by the TPF system, were required to control access to data shared by two or more processors in a loosely coupled complex. CF record lock support provides the option of using one or more CFs as XLFs.

CF record lock support offers significant flexibility for using CFs as XLFs in your locking configuration. The CFs in your locking configuration can be used either in addition to or instead of LLF and CFLFs. In addition, the CFs in your locking configuration can be used simultaneously for nonlocking workloads. The use of CFs in a locking configuration can eliminate the need for LLF or CFLF, giving you greater flexibility when selecting and implementing new module control units (CUs).

You can use CF record lock support to control access to data that is currently shared by two or more processors in a loosely coupled complex by now directing that workload to a CF. CF record lock support uses a logical locking mechanism as a means for serializing data access and processing steps to ensure the consistency and integrity of data records.

Logical Record Cache Support

A logical record cache provides you with high-speed access to data that enables you to develop data sharing programs with improved performance. A logical record cache can be processor shared or processor unique. Processor shared logical record caches exploit CF cache support to operate in a loosely coupled complex. With logical record cache support you can use a processor shared logical record cache for the following:

See TPF Application Programming for more information about logical record caches.

In addition, you can access and manage logical record caches by using the ZCACH command, and you can manage CF cache structures by using the ZCFCH command. See TPF Operations for more information about the ZCACH and ZCFCH commands.