COBOL Manual for TNS/E Programs (H06.08+, J06.03+)

Usage Considerations:
• Record Key
The data description entry for reckey cannot contain an OCCURS clause.
• Alternate Record Keys
The records within the file can be accessed in ascending order of the alt-key value. The
order in which records are obtained using alt-key can differ from the order obtained using
reckey. You can define up to 31 alternate keys for a file.
If you include the DUPLICATES phrase in the ALTERNATE RECORD KEY clause, the value of
alt-key need not be unique for each record in the file. Depending on the INSERTIONORDER
parameter of the alternate key file, records with duplicate alternate key values are inserted
(or retrieved) in either prime key order or in the order in which they were inserted in the file.
The data description entry for alt-key cannot contain an OCCURS clause or be subordinate
to an entry that contains an OCCURS clause. The leftmost character position of an alt-key
item cannot correspond to the leftmost character position of the reckey item or another
alt-key item in that file.
The file-control entry can contain at most one ALTERNATE RECORD KEY clause that describes
a particular alternate record key of the file.
If a file in the file system is defined as having alternate record keys to which the COBOL
program does not make any reference, you do not need to specify them in the File-Control
paragraph.
• Sequential Block Buffering
Sequential block buffering, enabled by the RESERVE clause when the file is open in INPUT or
I-O mode, is discussed under File-Control Entries for Sequential Files.
• Buffered Cache
Buffered cache, enabled by the RESERVE clause when the file is open in OUTPUT, I-O, or
EXTEND mode, is discussed under File-Control Entries for Sequential Files.
• HP COBOL Fast I-O (Local Buffering)
HP COBOLFast I-O is an enhancement in input-output performance beyond that of sequential
block buffering or buffered cache. It is available if the files upon which HP COBOL Fast I-O
is to operate meet the criteria under File-Control Entries for Sequential Files.
• Performance Penalty for Poorly Organized Indexed File
If a large number of entries have been added to and/or deleted from an indexed file, accessing
its records in sequence requires a significant amount of random processing; therefore,
performance suffers.
Input-Output Section 135