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Linkage methods SSL
156 U929-J-Z125-9-76
● Deletion
UDS/SQL must find the record to be deleted and also the record preceding it. This
requires less time if backward chaining has been specified. In the case of backward
chaining, UDS/SQL must also update the pointer in the subsequent record. If ORDER
IS SORTED INDEXED, the entry made for this record in the sort key table must be
deleted.
● Result
MODE IS CHAIN allows fast sequential access if the records are processed in the
sequence defined in the ORDER clause.
If the ORDER clause specifies SORTED INDEXED, fast direct access is possible even
in large set occurrences. If ORDER IS SORTED is specified, insertions are slower and
depend on the number of member records in the set occurrence. Modifications of the
primary key are relatively time consuming.
If the order of the member records is immaterial, the fastest mode of storing records is
achieved by specifying MODE IS CHAIN and ORDER IS NEXT or ORDER IS FIRST.