gtpg1m0o | General Information |
The TPF 4.1 system separates and isolates information into types of address spaces. The two major address spaces are for system processing and message processing. In the TPF 4.1 system, each message has its own address space.
Through the use of the dynamic address translation (DAT) facility and low address protection, the TPF 4.1 system changes how storage is physically and logically used for system programs, application programs, and messages.
The DAT facility provides a virtual storage environment for the running program and detects whether the program is storing into address spaces other than its own. Each message has private storage, both above and below 16-MB line that is not accessible by other transactions. However, message information that needs to be shared can be shared by other messages through common storage below 16-MB. The TPF system uses the DAT facility to provide each message with private areas that cannot be damaged by other messages or by the TPF system when it operates on behalf of other messages.
This program isolation prevents some of the storage-sharing techniques used in previous releases. However, messages can still share common information in storage through a pool of working storage below 16-MB called the common area.
The low address protection facility protects the first 512 bytes of storage against any alteration by an application program or the TPF system regardless of the storage key used.