Interpreting CASA output

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Hints, Tips, and Tricks

Sometimes, the output from CASA can be a bit cryptic. On this page, we detail some of the outputs from common tasks that might not be so intuitive. As with AIPS and other packages, some cryptic messages end up being benign messages for debugging purposes, while others are more significant. Of course, any feedback which crashes your script, or CASA itself, without any other discernable cause, is likely worth a visit to the Helpdesk, reachable through

How much progress have you really made?

For tasks that take significant time, you will often see a progress meter run across the screen from left to right:


In CASA, you will sometimes experience more than one such row, and potentially several for time- and labor-intensive tasks like clean. These are related to the subtasks which are being run. Short answer: seeing your first '100%' doesn't mean you're done. Getting the CASA prompt back does.

Don't be afraid of the QProcess

Sometimes you might see the following message:

QProcess: Destroyed while process is still running.

This can even happen when starting CASA initially, and is generally not reproducible. While this message sounds rather dire, it is a benign debugger message which you can safely ignore--it is just a result of lots of checks being put into place to check the status of the full range of processes that must run.

Table locks can be a pain

There are a number of messages you can get that indicate a table is in use; this usually means that you need to close the interactive task that is using the table before you can proceed. However, sometimes you can get really strange things happening:

2010-04-22 17:51:35     SEVERE          Exception Reported: Invalid Table operation: Cannot copy/rename; target table 
/export/data_2/username/data/archive/ is still open (is in the table cache)

Unfortunately, a message like this can even happen after you have deleted the MS file entirely! This really is (as labeled) a SEVERE error, and you will not be able to proceed if you insist on using that filename. There are a couple options.

First, try clearing the table lock manually:


If you still get the same error when you re-run your original command, you will likely need to exit CASA and restart.

Sporadic 'viewer' error

There is an error that can pop up without warning when you try to run viewer:

CASA <7>: viewer()
**** Error ****  'NoneType' object has no attribute 'cwd'


CASA <22>: viewer('raw.image')

**** Error ****  'NoneType' object has no attribute 'cwd'

This is an error the programmers have been trying to track down for some time, but it is hard to reproduce. Unfortunately, the only solution that works reliably is to exit CASA and restart. However, if you find a situation which can always produce this error, please contact the Helpdesk and provide them with some details.