File-Control Paragraph For Indexed Organization - IBM 5280 Programmer's Manual

Effects of Sequential and Random Access
You can access the record in an indexed file either sequentially (ACCESS IS
SEQUENTIAL) or randomly (ACCESS IS RANDOM).
With sequential access, the records are accessed in ascending sequence
according to the value of the record keys.
You can expect better performance with the sequential access method when:
• The file is being crea ted.
• The entire file is being updated, rather than just a few random records,
and a separate index data set hasn't been specified.
FILE-CONTROL Paragraph/or Indexed Organization
The following is a partial format of the FILE-CONTROL Paragraph:
SELECT file-name
ASSIGN TO DISK
["device-address1" ["[*volid1.]dsname1"]]
[INDEX "device-address2" ["[*volid2.]dsname2"]]]
[SIZE nnnn]
[SHARE
I
SHARER]
•
•
•
uNote: Other clauses in the FILE-CONTROL section include the
ORGANIZATION, ACCESS MODE, RECORD KEY, RELATIVE KEY,
and FILE STATUS clauses. They are described in the Language Reference
Manual; some are shown in the examples given later in this chapter.
Device-addressl, Volidl, and Dsnamel
The data set specified by this parameter contains the application records.
device-address 1 is the physical address (4000 or 4400, for example) or logical
address of the device on which the diskette must be mounted.
volidl is the identification given when the volume was initialized with the
diskette initialization utility.
dsnamel is the name given to the data set when it was allocated, usually
assigned with the diskette label maintenance utility.
The effect of the above specification on the prompt given when the program is
loaded, and the operator response to the prompt, is explained in the section
"FILE-CONTROL Paragraph" eailier in this chapter.
5- 22 IBM 5280 COBOL Programmer's Guide