File Management - IBM

Chapter 2. File processing
This chapter discusses basic aspects of processing files. Topics include:
v File operations supported by the system for use in high-level language programs
v File security considerations
v Sharing files in the same job
v Allocating file resources
v Temporarily changing a file when a program uses it
v Feedback areas maintained by the system
v Handling file errors when programs run
File Management operations overview
File management supports many operations that high-level language programs can
use to process data. These include the following, which are grouped by category:
v File Preparation
OPEN Attaches a file to a program and prepares it for I/O operations. A file
may be opened for any combination of read, write, update, or delete
operations.
ACQUIRE
Attaches a device or establishes a communications session for an open
file in preparation for I/O operations.
v Input/Output
READ Transfers a record from the file to the program. The data is made
available to the program once the read has been successfully completed.
WRITE
Transfers a record from the program to the file.
WRITE-READ
Combines the WRITE and READ operations as one operation.
UPDATE
Updates a record with changed data. The record must have been
successfully read prior to the update operation.
DELETE
Deletes a record in a file. The record must have been successfully read
prior to the delete operation.
v Commitment Control
COMMIT
Guarantees a group of changes are made as a complete transaction
across multiple records or multiple files.
ROLLBACK
Rolls back a group of changes to the point of the last commit operation.
v Completion
FEOD Positions the file at the last volume or at the end of data. For those
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