gtpc3m1s | Concepts and Structures |
Data records in the TPF system can be shared or isolated in several ways depending on the requirements of the user installation. This is achieved on the basis of record types.
Record types can be specified as shared or unique based on
For the sake of simplicity, unique and shared records are individually discussed in the context of subsystem user, I-stream engine, and processor. However, based on the requirements of the user installation, any combination can be specified, for example, subsystem user and I-stream engine unique.
In a TPF system generated with MDBF, record types that are defined as subsystem user shared are accessible to all subsystem users within a subsystem; that is, (1) there is one instance of each ordinal number of the record type and (2) all subsystem users must coordinate with each other to gain access to the record. Pool records are examples of record types that are subsystem user shared.
Record types defined as I-stream engine shared are accessible to all I-stream engines within a central processing complex (CPC).
Record types defined as processor shared are accessible to all CPCs within a loosely coupled complex.
In a TPF system with MDBF, any fixed record type can be declared to be subsystem user unique. Separate sets of records for a record type that is subsystem user unique exist for each of the SSUs of the subsystem. If the record type is not needed by all subsystem users of the subsystem, a set of records does not exist for those SSUs.
The ability to declare subsystem user unique records allows specific processing to be isolated within a subsystem user. The other subsystem users can be doing identical processing in parallel, keeping their data updates in their own sets of records. (See Figure 43.)
Figure 43. MDBF: One Subsystem, Two Subsystem Users. SSU Unique Records.
Because a TPF system can run in a central processing complex (CPC) with multiple I-stream engines, this same processing isolation is achieved on an I-stream engine basis by declaring certain record types as I-stream engine unique. See Figure 44.
Figure 44. Two I-stream Engines, One Subsystem. I-stream Engine Shared and Unique Records.
In a loosely coupled complex, processor unique records can be used to isolate data updates made by a specific CPC to a record that is only accessible by that CPC. See Figure 45.
Figure 45. Loosely Coupled Complex. Two CPCs, One I-stream Engine Each.