Tape Function Errors

Two common types of tape function error are covered in this section: parity errors, and an unexpected END OF RECORDED DATA message.

Parity Errors

Parity errors can occur for a number of reasons. Perhaps the most common cause of parity errors is using the wrong block size when copying to or from tape. Dirty tape drive heads can also cause parity errors. Or the tape itself may be bad—for instance, the heads used when writing the tape may have been dirty, thus corrupting the data on the tape at the time it was written.

If a parity error is detected during a file-restore, then percent signs are displayed (each % indicates a retry), along with the following prompt:

%%%%%%%%%% PARITY ERROR

(A) ACCEPT, (R) RETRY, (Q) QUIT

Parameter(s)

A	(ACCEPT) Skips the entire block with the error and moves to the next block.
R	(RETRY) Tries another ten times to read the data.
Q	(QUIT) Returns control to TCL without accepting the data.

Unless the file name is being displayed on the screen, it is not possible to determine which specific item and file has been affected except by judging the tape position and the current set of files which have not been completed.

CAUTION

If you type A and skip the corrupted block, there is no way of knowing what has been lost.

Unexpected End-Of-Data Message

Occasionally the following End-Of-Data message unexpectedly appears in response to one of the tape commands you enter:

[6000] END OF RECORDED DATA

If you suspect you are not at the end of recorded data on the tape, the most likely reason this message displays is that the wrong tape format has been specified. Use T-STATUS to check what the current tape format setting is. If the tape format is different from the one listed, use T-FORMAT to specify the correct tape format. T-FORMAT supports two modes of operation; RAW-ON and RAW-OFF.