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Schema DDL Types of access
U929-J-Z125-9-76 87
Dokuschablonen 19x24 Version 7.3us für FrameMaker V7.x vom 14.02.2007 © cognitas GmbH 2001-2007
24. Oktober 2007 Stand 09:30.23 Pfad: G:\vogt\fsc\uds\Manuale\en\udsent_e\udsent.k04
4.7.2 Generating additional access paths for direct access on record type
level
Defining a primary key for conversion by hash routine
LOCATION MODE IS CALC[ hash-routine]
USING item-name,... DUPLICATES ARE[ NOT] ALLOWED
With this clause, the user specifies the distributed storage of records on the basis of a hash
routine. The storage area which you address with this routine is called the hash area.
If the records are owners of a set, the corresponding set occurrences can also be conve-
niently selected (see the section “Determining set occurrence selection” on page 103).
A key declared by LOCATION MODE IS CALC is referred to as a CALC key. It is the primary
key for the record type. It may comprise several items (compound key).
item-name specifies the item(s) representing the key; all named items must belong to the
same associated record type and may be both numeric and alphanumeric.
With the DUPLICATES ARE[ NOT] ALLOWED specification, the user determines (for a
particular realm) whether UDS/SQL is to accept or reject duplicate key values.
Use hash-routine to specify the name of a module when you want to control the location of
the data in the hash area yourself. If you make no entry for hash-routine, UDS/SQL uses its
default hash routine.
If you have specified a hash-routine, it converts your primary key to a four-byte binary
number. UDS/SQL then converts the binary number to a relative page number. The page
with that number generally contains the associated record (see the section “Direct CALC
page” on page 210).