Linkage methods SSL
152 U929-J-Z125-9-76
Additional backward chaining for chain
MODE IS CHAIN LINKED TO PRIOR
In addition to standard forward chaining, the records of a chain can be con catenated in
reverse order. If LINKED TO PRIOR is specified, a further pointer is added to each record
pointing to the logically preceding record. In the same way as forward chaining, the pointer
is composed of the database key value of the preceding record and the PPP of the page
containing this record.
Figure 38: Additional backward chaining for chain
Backward chaining is important for large set occurrences where pr ior records are frequently
the object of a search.
Moore
.
. . .
Milk
.
.
.
. . .
Cocoa
..
. . .
Gin
..
. . .
Beer
..