gtps4m10 | System Generation |
Supported disk file storage devices are listed in the TPF Migration Guide: Program Update Tapes.
Disk file storage devices in a TPF system will typically contain approximately
98 percent of the database volume. The database may be divided into the
following areas. Note that the order of the areas in this figure is not
necessarily representative of the records on DASD.
Database Area | Duplication Status |
---|---|
Permanent Record Area | Not duplicated |
Core Image Restart Area (CIMR) | (Note 1) |
IPL Area | (Note 1) |
Keypoints - 4K Fixed Records | (Note 1) |
4K Application Programs, Fixed | (Note 2) |
4K Fixed Records | (Note 2) |
Large Fixed Records | (Note 2) |
Small Fixed Records | (Note 2) |
4K Long-Term Pool Records | (Note 2) |
4K Long-Term FARF6 Pool Records | (Note 4) |
Large Long-Term Pool Records | (Note 2) |
Small Long-Term Pool Records | (Note 2) |
4K Short-Term Pool Records | (Note 3) |
Large Short-Term Pool Records | (Note 3) |
Small Short-Term Pool Records | (Note 3) |
The primary facility to aid in maximizing the availability of records is record duplication. The amount of duplication is a function of how critical the information is to the system. Also to be considered is the ease of recreating lost data, volume of records of a particular type, and time spent to FIND or FILE duplicated records.
Thus, critical, highly used records and those difficult to recreate should be duplicated. Noncritical and/or infrequently used records and those which are quickly and easily recreated need not be duplicated. Records can be duplicated on file for immediate availability or they can be logged on tape and reloaded to effect recreation. It should be noted that there is a tendency by all users to fully duplicate all system records.
A user may choose any one of the following three alternatives for file layout:
Notes:
Duplication can include all records, no records, or selected areas. TPF uses the method of module-to-module duplication. Module-to-module duplication provides for an optimum seek time by allowing for greater flexibility in positioning records on the module. It is the easiest method to initialize. Module-to-module duplication can be utilized only with configurations which have (including planned growth) an even number of modules.
Figure 13. File Duplication Methods
There are two basic principles in minimizing the access time. The first is to spread the access load evenly across all modules and the second involves minimizing the access time for each individual module.
The access load is spread evenly across the modules by allocating an equal portion of each record type on each module. Thus, for an n module system, each module contains 1/n of the records of a particular type.
The second objective, for example, minimizing the access time for a module, is achieved with the following considerations: