# jCL F-UREAD

Updated: 10/19/2020, 10:24:56 AM
Created: 10/19/2020, 10:24:56 AM
Last Updated By: Daniel Klein
Read Time: 1 minute(s)

Tags: buffer file uread jcl

# Description

This command reads and locks a record from an open file into a file buffer. It takes the general form:

F-UREAD file-buffer key error-cmd-line
1

or

F-UR file-buffer key error-cmd-line
1

where:

  • file-buffer is the number (1 to 9) of the file buffer with which the file is associated.
  • key is the key of the record to be read and locked. Can be a literal (not enclosed in quotes), or a direct or indirect reference to a buffer or select register.
  • error-cmd-line is the line immediately after the F-UREAD command. Only executed if the specified record cannot be read.

The F-UREAD command is identical to the F-READ  command, except that it also locks the record against access by another process, thus eliminating simultaneous updates. Any attempt to F-UREAD a record which is already locked will be suspended until the other process unlocks the record. Record locks are released by F-DELETE, F-WRITE  or F-FREE commands, or when the program terminates.

# Note

It is good practice to F-UREAD a record before you create it. This will reserve the key in the file and avoid double updates. Remember though that the command line immediately following the F-UREAD command will be executed because the record does not exist.

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