This key allows access to the data on the tape. Many functions are controlled by the capability mask. Different copies of the TAPEKEY will produce access keys with different capabilities.

The tape access key transmits data to the requestor in records. These records may be blocked and unblocked into and out of tape blocks according to the format specified. This makes tape operations transparent to the requestor. All error recovery is handled by the access key.

NOTE! When variable and variable blocked formats are specified, the length of the data passed to the ACCESS key must be 4 bytes shorter that the specified record length in the format. The format is specified as an OS system will see the tape. OS type control words are added to the records by the ACCESS key so the user need not worry about such things. However the actual data must be 4 bytes less than the specified record length and the block length must be at least 4 bytes longer than the record length as there is a block control word added by the ACCESS key.

TAPEACCESS(kt ==> x'52b')

TAPEACCESS(0,(2,file #) [(1,F^V^U)][(2,BLKSIZE)][(2,LRECL)]; ==> c) OPEN a file for input.

The tape is positioned to the file number specified. If the tape is labelled, the header information is used as the file format . If the tape is unlabelled, the format information is taken from the TAPEKEY or the string specified on the call.

Not all of the format information needs to be specified. Starting from the left only that portion that the caller wants changed needs to be specified. If only the record format is specified then the block size and record length will remain at the default settings (fixed blocked 80/3200). If the block size is to be changed then specify the format and the blocksize.

Return codes

c = 0 done

c = 1 read rights restricted.

c = 2 The tape drive access key has disappeared either because of a Gnosis restart or a non-recoverable error in positioning.

c = 3 There is already a file open on this tape.

c = 4 bad format specifications.

c = 5 file number not specified as 2 bytes (less than 2 bytes on call).

c = 6 File requested is beyond the end of the tape (passed two consecutive file marks).

c = 8 unrecoverable read error in headers

The tape is positioned to the file number specified. A new file will be written at this point and become the last file on the tape. The filename and format information are used to construct the header records if the tape is labelled. Only that portion of the format that needs to be changed (starting from the left) needs to be specified.

The filename is included on calls for open of unlabelled tapes for compatibility. The caller need not know if the tape is unlabelled.

Return codes

c = 0 done

c = 1 read rights restricted.

c = 2 The tape drive access key has disappeared either because of a Gnosis restart or a non-recoverable error in positioning.

c = 3 There is already a file open on this tape.

c = 4 bad format specifications.

c = 5 file number not specified as 2 bytes (less than 2 bytes on call).

c = 6 attempt to position beyond the end of the tape

c = 7 Tape was mounted without a ring.

c = 8 unrecoverable read error in headers (for disp = MOD)

For labelled tapes only. The tape will be searched for the file name specified.

Return codes

c = 0 done

c = 1 read rights restricted.

For labelled tapes only. The tape will be searched for the file name specified. This file will be overwritten and become the last file on the tape.

Return codes

c = 0 done

c = 1 write writes restricted.

The previously opened file is closed. If the file is opened for output, trailer labels will be written as this file is the last file on the tape. For unlabelled tapes, several file marks will be written. The tape position is left so that a file opened with the next sequential file number can be written without repositioning the tape.

Return codes

c = 0 done

c = 2 The tape drive access key has disappeared either because of a Gnosis restart or a non-recoverable error in positioning.

c = 3 No file is open

Up to 4096 bytes of data is transferred to the tape. If blocking has been specified in the format information, then the data is first blocked before writing to the tape.

If the tape is unlabelled and this is a write at loadpoint, the label verification is calculated and stored in the TAPEKEY.

For Unlabelled tapes, the first block may not appear to be a label. It may not be an 80 byte record with the first 4 bytes "VOL1". The density is set on the drive if the tape is unlabelled and the first record is written.

When End of Tape is indicated, the file is closed indicating end of volume. To continue, call TAPEKEY to mount the next volume, and ,if successful, call TAPEACCESS to open file 1. Attempts to write records after an End of Tape without following the above procedure will result in return code 3.

Return codes

c = 0 done

c = 2 The tape drive access key has disappeared either because of a Gnosis restart or a non-recoverable error in positioning.

c = 3 Tape is not opened for output.

c = 4 Record length error (incorrect length on fixed blocked, or more than recordlength-4 for variable).

c = 5 End of tape encountered (switch reels or close file).

c = 6 Unrecoverable error on write (after many erase gaps)

c = 7 Drive not capable of the density in the default format

c = 8 first record of unlabelled tape looks too much like a label.

Up to 4096 bytes of data is transferred from the tape. Unblocking is controlled by the format information. NOTE! the data may be truncated if the requestor does not accept all the data.

When the End of Tape return is made, the file is closed. To continue reading (for multivolume files), call the TAPEKEY to mount next volume and call TAPEACCESS to open file 1. Attempts to read without doing the above will result in return code 3.

Attempts to read after End of File will result in repeated End of File indications.

Return codes

c = 0 done

c = 2 The tape drive access key has disappeared either because of a Gnosis restart or a non-recoverable error in positioning.

c = 3 file not opened for input

c = 4 Record length error (actual tape block not agree with blocksize).

c = 5 End of Tape

c = 6 End of File

c = 8 Unrecoverable error on read (data is supplied as read)

c = 16 For format U records only. Record (block) exceeds 4096 bytes. 4096 bytes will be returned on this and subsequent requests until the return code is 0 (or some error).

The tape is rewound to loadpoint, and the TAPEKEY is updated to reflect the unlabelled status of the tape. The first block is read and the verification checksum is stored in the TAPEKEY. Subsequent writes at load point will update the verification checksum.

Any tape that is not part of a multivolume set may be made unlabelled. After such an operation, the labels on the tape may be read or overwritten. The tape may be returned to its status as labelled only by a write label operation.

The first block written on an unlabelled tape may not look like a label.

Return Codes

c = 0 done

c = 1 make unlabelled rights restricted

c = 2 The tape drive access key has disappeared either because of a Gnosis restart or a non-recoverable error in positioning.

c = 3 tape is currently open.

c = 4 TAPEKEY is for a multivolume set

c = 5 first file is null

c = 8 first record is unreadable

The first block of the tape after load point is read and verified according to the label type.

Return codes

c = 0 ok Label valid

c = 1 rights restricted

c = 2 The tape drive access key has disappeared either because of a Gnosis restart or a non-recoverable error in positioning.

c = 3 Label not valid (wrong tape mounted).

Standard ANSI labels are written on the tape. The Volume ID of the tape is taken from the TAPEKEY.

Return codes

c = 0 ok

c = 2 The tape drive access key has disappeared either because of a Gnosis restart or a non-recoverable error in positioning.

c = 3 write label failed.

c = 4 not a single volume TAPEKEY

c = 5 File open on on this tape

c = 7 Drive not capable of the density in the default format

c = 8 Cannot write label on a tape after a Makeunlabelled operation.

When a tape is introduced, the label type must be determined and the label type set. This operations calculates the checksum of the first block and records it in the tapekey node.

Return codes

c = 0 ok

c = 1 rights restricted

c = 2 The tape drive access key has disappeared either because of a Gnosis restart or a non-recoverable error in positioning.

c = 3 Standard label has incorrect volume id (does not agree with Reel Number in tapekey).

The error log is returned. Each entry is 32 bytes long and contains the CSW and Sense information. The first entry is a dummy and contains only the relative address of the current entry in the first 4 bytes.

A sense is issued and the data is returned. CSW is of the form (1,cc)(3,ccw-offset),(2,status),(2,residual-count).

Any pending interrupts are cleared before the sense is issued. This is intended to be used by the Tape Operator to sense whether a ring is in the tape after a mount. The pending interrupt is cleared because it is expected after the mount (device end).

Return codes

c = 0 sense done

c = 2 tapedrive access key has disappeared due to a Gnosis restart.

The tape is unloaded. This is used by the Tape Operator after a restart and before each mount (if the correct tape is not mounted already).

Return codes

c = 0 done

c = 1 not allowed

c = 2 tapedrive access key has disappeared due to a Gnosis restart.

The tape density is set based on the density code in the TAPEKEY.

This is not of much use. The function may be expanded. The density currently is set whenever the first block is written on the tape.

MODE is a character of one of the following: "2" - 800 bpi, "3" - 1600 bpi, "4" - 6250 bpi, "5" - future density.

CSW and SENSE are present if the operation gets either unit check or unit exception.

Return codes

c = 0 done

c = 1 not allowed

c = 2 tapedrive access key has disappeared due to a Gnosis restart.

c = 3 mode is not 1 byte

c = 4 mode character invalid

c = 5 I/O error csw and sense present

For opens of files for output, adding 16 to the order code causes the tape to be positioned at the end of the opened file.

Return codes

See various OPEN requests.