11.2 Exiting from

Before ending a period of data reduction with , you should back up those data files which you wish to keep, delete all of your disk data files, tidy up your work area, and then issue the KLEENEX (to stop the TV, Tek, and message servers too) or EXIT (to leave the servers running) command to the AIPS program. Of course, if the computer and disks are part of your very own workstation in your office, you may ignore all this advice. Backups on magnetic tape used to be a good idea, but there are few if any such devices now available. Disk files are easily deleted due to software or user malfunction, or lost due to disk hardware malfunction.

Note that, when you exit AIPS you leave behind some nearly invisible files even if you have attempted to remove al of your data files. The “hidden” files are in your  data area number one and include message (MS), readline (RL), SAVE/GET (TG), and task data (TD) files. In 31DEC23, task CLNUP will list these files as well as data files older than a specified interval and will delete old “hidden” files. Old data files must be deleted using ZAP or ALLDEST.

11.2.1 Backups

While processing and particularly just before exiting from , please delete as many of your own data sets as possible. Images and uv data may be backed up on disk in FITS format using the task FITTP. This task can write only one disk file at a time; tapes were more cooperative. For example, to backup a uv file, type

The FITS format used for plot files will not be useful to any software other than , but it does allow saving the plot files for later use in . The RUN file WRTPROCS contains two procedures to assist in writing more than one  data set or image to disk. FITDISK generates the full DATAOUT from an input DATAOUT and the  file name. WRTDISK generates the full DATAOUT from an input DATAOUT and the  disk and catalog numbers. These procedures and FITAB support the plot file option.

Task FITAB also writes FITS disk files. For uv data it has the advantage of being able to write the data in compressed form, saving disk space, and of writing the data in multiple “pieces” for increased reliability. Unfortunately, the table form of data used may not be understood by other software systems. Note that FITAB is used for processed uv data by the NRAO archive — it will matter to many users to update to a modern release. FITAB may apply a quantization to images on output that allow the FITS files to be compressed very much more efficiently. If the quantization level is set below 1/4 of the image noise, then the noise in the output image will only be 1–2% larger than in the input image.

11.2.2 Deleting your data

Please delete redundant images and data as soon as possible to preserve disk space for yourself and other users. It is tempting to work on many sets of data at the same time, but this generally takes a lot of disk space and users should limit the amount of data resident on disk to that which will be processed during the session. A data set and all extension files can be deleted by:

To delete data in contiguous slots from n to m in a catalog, set the INDISK and use the loop:

For massive deletions — the kind we hope you will use when you leave an NRAO site — use:

And to compress your message file, after using PRTMSG to print any you want to keep, use:

DO NOT DELETE OTHER USERS’ DATA OR MESSAGES WITHOUT THE EXPLICIT PERMISSION EITHER OF THE OTHER USER OR OF THE AIPS MANAGER.

11.2.3 Exiting

To exit from AIPS type:

Please clean up any papers, tapes, etc. in the area around your terminal before you go.