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88 U929-J-Z125-9-76
If you want to define a user-specific hash routine, you must observe the following register
conventions:
● Before and after running the routine, all UDS/SQL registers except Register 1 must
have the same content.
The hash routine is branched to by BALR 14,15; return to the UDS/SQL hash routine is
effected by BR 14.
● The following information is provided by the UDS/SQL DBH:
Register 1: The address of a word containing the address of the key item
Register 2: The address of a byte containing the length of the key item.
Register 3: The address of a word containing the number of pages of the hash area
assigned to this key.
Register 13: Starting with the address (Register 13) + X’0C’, 13 words are available
to the user as a transaction-oriented save area for registers.
● The UDS/SQL DBH expects the result of the hash routine in Register 1. It converts the
binary number encountered there into a relative page number as follows:
–Bit 2
31
in Register 1 is set to 0.
– If the resulting value is less than the number of pages in the hash area (content of
Register 3), this value is used as the relative page number.
– If the resulting value is greater, UDS/SQL performs the following division:
content (Register 1) / content (Register 3)
The quotient of this division is used as the relative page number.