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Population SSL
138 U929-J-Z125-9-76
Size of a hash area for the primary key
POPULATION IS {integer WITHIN realm-name},...
The hash area for the primary key of a record type is distributed over several realms if the
records of the record type are allocated to several realms by means of the schema DDL
(see the section “Defining allocation of records to realms” on page 110).
integer specifies the number of records to be stored in the realm referenced by realm-name.
Using this number, UDS/SQL calculates the minimum number of pages required for storing
the records (see the section “Direct CALC page” on page 210) or the record addresses (see
the section “Indirect CALC page” on page 213) in the respective realm. In each realm,
UDS/SQL then reserves a number of pages corresponding to the next higher prime number.
A hash area is extended by means of overflow pages if the data assigned to a page by a
hash routine exceeds the maximum capacity of the page. The overflowing page is linked to
the overflow page by means of act-keys.
The efficiency of a hash routine can be judged by how evenly it distributes data over the
hash area, i.e. how many overflow pages are generated.
A hash area can be subsequently extended by means of the BREORG utility routine (see
the "Recovery, Information and Reorganization" manual, BREORG).
By default, UDS/SQL sets up a hash area of one page.
Example
DDL:
RECORD NAME IS ARTICLE
LOCATION MODE IS CALC
WITHIN CLOTHING, HOUSEHOLD-GOODS, ..... AREA-ID .....
.
.
.
SSL:
RECORD NAME IS ARTICLE
POPULATION IS 400 WITHIN CLOTHING, 100 WITHIN HOUSEHOLD-GOODS, .....