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General InformationAIPS users should know the following tidbits:
AIPS and Tapes at the AOCTape NumberingAll public workstations and a number of other workstations have tape drives attached to them. Within AIPS, each of these drives is assigned a number, and is referred to using AIPS adverbs such as INTAPE and OUTTAPE. A list of the available drives and their associated numbers is given on AIPS startup, or, within AIPS, by typing TAPES. For instance, on a typical machine with one Exabyte drive attached to it, the TAPES command gives:
INTAPE 1 is the local Exabyte drive, INTAPE 2 and 3 are for filling ongoing observations at the VLA, and INTAPE 4 and 5 are used to access drives on other workstations ( see Remote Tape Access below). Local Tape AccessFor an AIPS task or verb to access a tape drive, the drive has to be mounted using the AIPS verb MOUNT, e.g., INTAPE 1
Always make sure to issue the MOUNT command well after physically mounting the tape: many drives need 30 seconds or so to get ready for access. Remote Tape AccessIn order to access a tape on a remote machine
If all is well, this should be followed by a one-line message of the kind: AIPS 1: Mounted on ANSI SCSI 2 tape (EXB-8500) on host alfirk. TPMON processesIf upon MOUNT you get a list of error messages instead of the single line of the type above look in the next section for a list of common problems. Some of those problems can be fixed by manipulating the TPMON processes on the remote machine. For remote access to work, the machine with the remotely accessed drive requires the presence of n active processes TPMON1 through TPMONn, where n is the number of physical drives on that machine + 1. Killing and/or restarting TPMON processes can sometimes solve remote tape access problems. Common remote tape problems after MOUNT
The drive is in
use by someone who failed to do a DISMOUNT in AIPS before unloading the tape.
Some or all TPMON processes are not running. Log on to the remote machine and restart the TPMON processes (see next Section).
Some or all
TPMON processes are corrupted. Log on to the remote machine and kill and restart the
TPMON processes
The tape in the
drive is not ready yet, or there is no tape in the specified drive.
Killing and restarting TPMON processesIn some of the cases above TPMON processes had to be killed and restarted. In order to do so, log on to the remote machine *as AIPS* (this is very important) using ssh machinename -1 aips and type ps -elf | grep TPMON. If the TPMON processes are not all there, starting AIPS on the remote machine will restart them. Even if they are all there, sometimes the processes need to be killed and restarted. To kill the processes type kill n1,n2,n3 where n1,n2,n3 are the process ID numbers. Then, still on the remote machine, restart the TPMONs by starting AIPS. The system may complain you don't have a valid AIPS number, but the TPMON processes will be started anyway. If you are unable to kill the TPMON processes check the owner of the processes listed in the first column after the ps -aux | grep TPMON command. If you are not logged in as that owner, either track down the owner and ask him/her to kill the processes or contact the Helpdesk to do this for you. For this reason, on public machines, it is important you restart any TPMON processes while logged in as AIPS, not as yourself. This will allow others logged in as AIPS to kill these processes at a later date, if needed. Other tape problemsOther tape problems may occur regardless whether access is remote or not. When occurring parity errors, particularly when using Exabyte drives, the heads may be misaligned with the heads of the drive that wrote the tape. The solution is to try another drive. When reading or writing is very slow, and the read-out window labeled % Rewrites on the front of the drive shows numbers over 5, the heads are dirty and need to be cleaned. Sometimes running a cleaning tape, obtainable from Gayle Rhodes, AOC 267, helps, but often more substantial cleaning is required. Contact the Helpdesk when this is the case. In case of any other tape related problems contact us! Author, Gustaaf van Moorsel
Copyright © 2009 Associated Universities, Inc. Content reviewed on: 03-October-2006
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