Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (H-K)
Guardian Procedure Calls Reference Manual—522629-013
7-62
KEYPOSITION[X] Procedures
(Superseded by FILE_SETKEY_ Procedure)
When saving the current position in a relative or entry-sequenced file with no
alternate keys, the SAVEPOSITION procedure requires an additional three words
in the
positioning buffer, for a total of seven words when read-reverse
positioning is in effect. If you have programs currently using SAVEPOSITION with
a four-word
positioning buffer, please note this change.
•
Read-reverse action on current and next record pointers
Following a call to READ when reverse-positioning mode is in effect, the
next-
record-pointer contains the record number or address which precedes the
current record number or address.
Following a read of the first record in a file (where
current- record-pointer
= 0) with reverse positioning, the
next-record- pointer will contain an invalid
record number or address since no previous record exists. A subsequent call to
READ would return an “end-of-file” error, whereas a call to WRITE would return an
“illegal position” error (error 550) since an attempt was made to write beyond the
beginning of the file.
•
KEYPOSITION and file-system error 21
If any of the following conditions are true, error 21 is returned by KEYPOSITION:
•
If the primary file is a key-sequenced file and one of the following is true:
•
key-specifier is omitted or 0 and key-length is greater than the key
length defined for the primary file.
•
compare-length is greater than key-length.
•
If the key-specifier is not zero and one of the following is true:
•
key-length is greater than the sum of length of the alternate-key field
and the length of the primary key of the file.
•
key-length is less than or equal to the length of the alternate-key field,
and
compare-length is greater than key-length.
•
key-length is greater than the length of the alternate-key field and the
primary file is not key-sequenced, and the difference of
key-length and
compare-length is less than 4.
•
key-length is greater than the length of the alternate-key field and the
primary file is not key-sequenced, and the
key-length is less than the
sum of the length of the alternate-key field and the length of the primary
key of the file.
•
KEYPOSITIONX error
In addition to the errors returned from KEYPOSITION, error 22 is returned from
KEYPOSITIONX in either of the following cases:
•
the address of the key-value parameter is extended, but no segment is in
use at the time of the call or the segment in use is invalid.