COBRT034 Incorrect mode or file descriptor (Recoverable)

You are either trying to write to a file which is open for read purposes only, or read a file which is open for write purposes only.

Resolution:

You should close the file and reopen using the correct access mode. As this error implies that your program logic contains a mistake, you might want to close any open files, execute a STOP RUN statement and then recode your program to eliminate the logic error.

Shareable files opened INPUT (read-only) by the COBOL system still require write-permission (from the operating system) to enable temporary locking to take place.