gtpd1m0cDatabase Reference

Online Database Addresses

The file address that the FACE program or the get file storage macros generates for use with find or file type macro requests exists in one of the following formats:

Figure 1 describes these formats.

Note:
In this chapter, the term FACE is used as a generic name for the FACE, FACS, FACZC, or FAC8C program.

Figure 1. File Address Formats


FARF Format

With FARF addressing, a database ordinal number is recalculated each time the find and file type macros find the format that represents a record type and ordinal number; the configuration dependencies are bound to channel programs that are based on their current assignments and held in the FACE table (FCTB). This means that imbedded addresses that use FARF format are less sensitive to file reorganizations because of the late binding of the referenced imbedded address to the actual physical address of the record.

Nevertheless, data must be moved to correspond to any new allocations. This is done by a TPF capture of online data using the directories and FCTB of the original allocation. This is then followed by a TPF restore using the directories and FCTB of the new allocation.

The first of the FARF formats is file address reference format 3 (FARF3) and is shown in Figure 1. Based on the sizes of the band and ordinal number fields in a FARF3 fixed address, there are 212 bands and 216 ordinals. This yields an addressing range of as many as 228 (268 435 456) fixed records. Mapping FARF Addresses explains the methods and reasons for assigning band numbers to fixed records.

There is no band field in a FARF3 pool address. Each pool record that is defined in the TPF system is related to a record type based on pool type, size, and duplication. The bits in the FARF3 pool address indicate which type the address belongs to. Each pool record type can have as many as 226 records because 26 bits is the length of the ordinal number field.

The FARF4, FARF5, and FARF6 formats are also shown in Figure 1. FARF4, FARF5, and FARF6 addresses make no distinction between fixed and pool addresses. With 2 bits of a FARF4 address delegated to control information, this provides an addressing space of 230. FARF5 has no control bits reserved in the address, so 232 (4 294 967 296) addresses can be represented. FARF6 can represent 256 addresses (72 057 594 037 927 936). All control information for FARF5 and FARF6 addresses is found in the FACE table. The dividing line between the format type indicator (FTI) field and the ordinal field in FARF4, FARF5, and FARF6 addresses is not in a fixed position. For each universal format type (UFT) value, a different FTI size can be related.

Note:
The UFT is 6 bits for FARF4 and FARF5 (64 possible UFT values). For FARF6, the UFT is 16 bits (65 536 possible UFT values).

Once the FTI size is known, the FTI value, the ordinal size, and the ordinal value can be determined. Mapping FARF Addresses describes how these values relate to specific ordinal numbers of a record type.