Label Anomaly Exit (IFG019LA)

The system calls this exit when it has found one or more certain unusual conditions on a tape. With the dummy version of this exit most of these conditions cause OPEN or EOV to go to the label editor routine or to issue ABEND (possibly after calling the user's DCB abend exit). The label editor routine is documented in Volume Label Verification and Volume Label Editor Routines. IBM recommends using the label anomaly exit instead of a label editor routine for the reasons stated in the label editor sections.

The label anomaly exit will receive a UCB address from TEPMUCB in IFGTEP, from DEBUCBA and from TIOEFSRT. All three sources will allow a 31–bit UCB address. TEPMICB will sometimes be an uncaptured 31–bit address. If the DEB31UCB bit is on, the UCB address and modeset byte will be different as described in IEZDEB. If they use the DCBTIOT field to find the TIOT entry address, they should be changed to use TEPMDSAB to point to the DSAB, which points to the TIOT entry or XTIOT.

These are the situations under which the system calls a label editor routine and the label anomaly exit:

Label type conflict. User opening for OUTPUT or OUTIN and the requested label type (SL, AL, NL, NSL) differs from the actual label type. If the exit gives return code 4 and turned off this anomaly bit and the requested type is SL or AL, then the exit has built a volume label in EBCDIC in the supplied area. OCE will verify that it begins with VOL1. The requested label type is in the JFCB. The exit can determine the actual label type by examining the first four bytes of the area to which TEPMLABEL points. It is in the main parameter list. The area is from the first block on the tape after load point. If it is not "VOL1", then the tape is not labeled or it has nonstandard labels. If it is "VOL1", then the label is SL or AL. To determine which, the exit can test bit TEPMASCII in the main parameter list.
Density conflict. User opening for OUTPUT, OUTIN, INOUT, OUTINX or EXTEND and the existing density differs from the requested density. The volume is mounted on a dual density drive. Return code 4 with this anomaly bit off means to use the requested density if writing file 1 or the existing density if writing a later file.
Volume serial conflict. The user is opening for OUTPUT or OUTIN and the mounted volume serial differs from the requested volume serial. With return code 4 and this anomaly bit off this exit can supply a new volume label.
Label version conflict. User opened for OUTPUT on an AL tape and the volume label is not for Version 3 or Version 4. With return code 4 and this anomaly bit off this exit can supply a new volume label.
Track conflict. The tape cannot be read because of incompatibility between the tape and the drive, not because of some other I/O error. The exit can test the CSW status bytes and the sense bytes in the main parameter list. See TEPMSENSE. One case is 36-track tape mounted on 18-track drive. TEPATRKC on indicates this condition. The volume serial number might have come from the sense bytes, in which case TEPMSYNV is on. A PARMLIB option controls what open, close, EOV does. For example, if DEVSUPxx parameter VOLNSNS=YES is specified, the OPEN or EOV label editor routines will rewrite the VOL1 label using the volume serial number obtained from the drive sense bytes. The LABAN exit can give permission to use the tape, which means that the system can destroy the labels without reading the labels. This means the exit is taking responsibility for such things as security and the files being expired. The exit can provide all the information to be written in the new volume label. The system will still call RACF for the volume but without the header label information. The IBM—supplied Label Editor routine, OMODVOL1 or EMODVOL1 will delete the RACF definition for the volume. The exit can bypass this delete of the RACF TAPEVOL profile when the system has set flag bit TEPABYRACF in byte TEPAFLAG3 indicating the bypass option is active. Setting flag bit TEPAEXSKIP in byte TEPAFLAG3 when TEPABYRACF has been set by the system, and returning return code 4 results in bypassing the delete of the RACF TAPEVOL profile.
I/O error. I/O error while reading volume label for output tape and RACF tape protection is not active. If the exit gives return code 4 with this anomaly bit off, the system tries to create a new label.

Those conflicts can also be handled by OMODVOL1 and EMODVOL1. Any conflicts you do not handle in the label anomaly exit are passed to OMODVOL1 or EMODVOL1 to handle. The following are not supported by OMODVOL1 or EMODVOL1:

Unsupported cartridge length Cartridge tape length exceeds IBM's maximum supported length for this drive. This call to the exit is for information only; the tape will be rejected even if the exit turns off the bit. This means to reject the tape if it is a nonspecific request or to issue ABEND if it is a specific volume request.
Writing unsecure checkpoint Writing a checkpoint to an unsecure tape, indicated by bit TEPACHKPT in byte TEPAFLAG1. Return code 8 from the exit means to reject the tape. This means to reject the tape if it is a nonspecific request or to issue ABEND if it is a specific volume request. Return code 8 can also mean that the volume is not secure. This code is like a reply of "NO" to the messages.
Return code 4 from the exit with the bit still on will result in one of these messages to the operator:
- IEC254D SHOULD jjj USE (ddn,uuu,serial) FOR CREATING A NEW CHECKPOINT DATA SET
- IEC255D jjj IS (ddn,uuu,serial) A SECURE CHECKPOINT VOLUME
Return code 4 and the TEPACHKPT bit set off results in the system assuming the tape is secure. This is like a reply of "YES" to the messages. If you write a non-checkpoint data set as the first data set on a checkpoint secure volume, then bit TEPANOCKPT is set in the exit's parameter list. When the exit returns a return code of 4, and when bit TEPANOCKPT is still on and it is not an Automatic Tape Library (ATL), then the system issues a scratch volume WTOR IEC255D. The system writes an ATL scratch volume's HDR2 and bypasses WTOR IEC255D. If the exit resets the bit TEPANOCKPT, then the system assumes that the volume is not checkpoint secure, does not issue message IEC255D, and behaves as if the operator had replied "NO" to message IEC255D.
Overwriting ISO/ANSI user volume labels User volume labels or ISO/ANSI Version 4 volume labels 2-9 are about to be overwritten.
Return code 4 with the bit on results in message IEC704A.

Return code 4 with the bit off results in the labels being overwritten.

Return code 8 means to reject the volume. This means to reject the tape if it is a nonspecific request or to issue ABEND if it is a specific volume request.
Writing volume label Volume label information is needed to write the label.
Return code 4 with the bit on results in message IEC704A.

Return code 4 with the bit off means that the exit has supplied the volume label. For volume serial number conflicts between the volume mounted and the volume requested, and for label type conflicts when an NL scratch volume is requested and a labelled tape is mounted, the volume serial number supplied by the exit will be used to either rewrite the volume label or to catalog the NL volume. In the latter case the system will not generate an Lnumber. In order for the label anomaly exit to supply a volume serial the following steps are required:
1. Reset TEPASERIAL (volume serial conflict) or TEPALTYPE (label type conflict) in byte TEPAFLAG1.
2. Set bit TEPMNEWLAB in byte TEPMFLAG6.
3. Provide valid volume serial number in field TEPMVOL.
See Label Anomaly Exit (IFG019LA) Return Codes.
Return code 8 means to reject the volume. This means to reject the tape if it is a nonspecific request or to issue ABEND if it is a specific volume request.
Multivolume tape conditions When reading an unexpected volume sequence number, a missing final volume, or a missing first volume (reading forward or backward) was encountered during multivolume tape processing. With return code C and the corresponding anomaly bit on, this exit issues a message and abends the job.
With DFSMSrmm, the missing or out of sequence conditions are normally resolved, which results in a complete volume list for the multivolume being processed. If you want to process only the original incomplete or out of sequence volume list, you can use a label anomaly exit to ensure the original volume list is used. The following example uses IFG019LA to ensure the original volume list is processed unaltered.
Figure 1. Example using label anomaly exit IFG019LA
IFG019LA CSECT ,
IFG019LA AMODE 31
IFG019LA RMODE ANY
         SPACE 2
         SAVE  (14,12)
         LR    12,15
         USING IFG019LA,12                 addressibility
         SPACE 2
EXIT     DS    0H
         USING TEPM,1
         L     3,TEPMTEP
         USING TEPA,3
         TM    TEPANMLY2,TEPASEQ           vol list out of seq
         BNO   CHKFML                      no
         OI    TEPAFLAG3,TEPAOUTSEQ        don't alter vollist
         B     EXITEXIT                    exit
CHKFML   TM    TEPANMLY2,TEPAFML           missing last volume ?
         BNO   CHKBML                      no
         OI    TEPAFLAG3,TEPARDFMLV        don't alter vollist
         B     EXITEXIT                    exit
CHKBML   TM    TEPANMLY2,TEPABML           rdback missing last
         BNO   CHKFMF                      no
         OI    TEPAFLAG3,TEPARDBMLV        don't alter vollist
         B     EXITEXIT                    exit
CHKFMF   TM    TEPANMLY2,TEPAFMF           missing first volume ?
         BNO   EXITEXIT                    no
         OI    TEPAFLAG3,TEPARDFMFV        don't alter vollist
EXITEXIT DS    0H
         DROP  3
         DROP  12
         L     14,12(,13)          restore return address
         LA    15,4                set continue return code
         LM    1,12,24(13)         restore callers regs
         BR    14                  return
         SPACE 2
         IFGTEP MAIN,LABAN
         END

For a particular OPEN or EOV this exit can be called more than once for various reasons.