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Frequently Asked Questions about the BIMA Data Archive

Don't see your question here? Email us at bimadata@ncsa.uiuc.edu.

Answers to Frequently Asked Questions

Q1. How can I submit questions/comments/bug reports to the maintainers of this archive?

Submit your questions by sending mail to the archivist via bimadata@ncsa.uiuc.edu.

Q2.How do I get my data from the Archive?

If you are new to the Archive, consult the instructions for first-time users. It explains the three basic steps necessary for setting up your environment for downloading data:
  1. Obtain a special username and password -- You must authenticate yourself in order to access data from the archive.
  2. Find or Install a download client (DaRT) on your system -- this is a program that helps you download many data files from the archive at once.
  3. Configure your Web browser -- you need to tell your browser to start DaRT automatically when necessary.
Next, you might want to consult the summary on using the Archive which describes how to search, browse, and retrieve data.

Q3. Do I have to use NCSA Mosaic to access the Archive, or can I use Netscape?

You should not use NCSA Mosaic nor its wrapper script, xmbima, as these are no longer supported. Netscape is the recommended browser to use with the Archive; however, in principle, any browser that supports tables will work.

Q4. Ack! When I use xmbima...

Do not use xmbima or NCSA Mosaic; these are no longer supported. Netscape is now the recommended browser (see also Q3). Consult the instructions for configuring Netscape for use with the Archive.

Q5. When I press "Retrieve Selected Datasets", I get a small file with a list of URLs in it. Where is my data?

This indicates that your browser is not properly configured to access the archive. Consult the instructions for first-time users. When your browser is set up properly, pressing the Retrieve button will cause the DaRT application to start which will allow you to choose a destination directory for the data. When you tell DaRT to commence the download, DaRT will use that list of URLs to retrieve your requested datasets and unpack them onto your disk.

Q6. What is this Dart program I keep hearing about? Why should I use it (instead of xmrecvlist)?

DaRT stands for Data Retrieval Tool and is a replacement for xmrecvlist. An archive user sets up their browser to run DaRT as a helper app that starts up automatically whenever multiple datasets are requested for downloading.

Archive users are encouraged to use DaRT instead of xmrecvlist for three reasons:

  1. DaRT is much more flexible than xmrecvlist. DaRT allows you to choose where to store the downloaded data; with xmrecvlist, the data will be stored in the directory from which you started Netscape. Furthermore, DaRT gives you much more control over which data you actually download and when you do it.

  2. DaRT provides a nice GUI while xmrecvlist is silent about its work. With xmrecvlist, it's not obvious when it is working properly. More importantly, it's even less obvious when it has finished downloading the data. When it does fail, the error messages are cryptic. On the other hand, with DaRT's GUI, you explicitly start the download when you are ready (or you can save it for later). It provides indicators that show the download process. When something fails, the error log is more informative; furthermore, error logs can be emailed to us directly from DaRT, allowing us to more easily address any problems.

  3. xmrecvlist is being phased out. xmrecvlist will not be able to handle processed data from the BIMA Image Pipeline; thus, we will eventually stop supporting xmrecvlist as a method for retrieving data.

See the instructions for first-time Archive users to set up your browser to use DaRT. For more information about DaRT's capabilities, see the DaRT Home Page.

Q7. I don't know DaRT from xmrecvlist. How do I tell which one I'm using?

Try running the following command: 
    grep x-multiget $HOME/.mailcap
If you see something like, 
    application/x-multiget; $MIRBIN/xmrecvlist %s
then you are setup to use xmrecvlist. Note that the pound sign (#) is a comment character; any lines produced from the above command that begin with this character have been commented out. If you see something like, 
    application/x-multiget; /usr/local/bin/dart %s
then you are setup to use DaRT.

When you request files for download, it will be obvious if DaRT is properly set up. The DaRT welcome image will appear on your screen, followed by the main GUI window. With xmrecvlist, it's less obvious when it is working properly. When it starts up, a message will appear at the bottom of your Netscape window saying something like "launching xmrecvlist...".

Q8. When I use the the single item retrieval method (clicking the "Download" link), it sometimes takes a very long time to even begin retrieving the dataset. What's going on?

This generally means that the dataset you requested needed to be retrieved from the Mass Storage tape system. This can take anywhere from 2 min to 15 minutes to get a response. I am afraid that is just the nature of the beast. However, if you are regularly waiting more than 10 min for such a retrieval or if you are encountering other problems, please send email.

Q9. There is a red message in the Dart Window that says there are new error messages. What should I do?

Select "View->Error Log" to bring up the error log window. This will list all of the error message produced so far. If you need help dealing with the problem (e.g. because they appear to be due to server problems) feel free to mail the log to us by pressing the "Mail" button.

Q10. How do I know that xmrecvlist is working properly?

Note: xmrecvlist is being phased out; we recommend that you reset your browser to use DaRT; see the instructions for first-time users for details about doing this.

First, here's what should happen during normal operation, assuming that you are using Netscape to access the archive. Suppose that you conducted a search which produced a list of tracks or datasets matching your query. You check off the datasets you want, and then you click "Request Selected Items". First you see a message at the bottom of your screen saying "Done sending HTTP request; waiting for response..."; after a bit it will say "Spawning external viewer". This second message indicates that xmrecvlist has started.

To confirm that xmrecvlist is actually working you can do one or more of the following:

  1. In the directory that you started xmbima from, look for a directory named after the observation year for the data that you requested (e.g. 97 for data observed in 1997). Unless it already existed, this was created by xmrecvlist. Examine the contents of this directory; you should see your datasets beginning to appear under a directory structure of the form year/month/day/project/dataset.

  2. You can look for the xmrecvlist processes running on your system using ps or top. For example, on a Sun running Solaris, you could type:

    /usr/ucb/ps -auxww | grep xmrecvlist
    You should see one or more instances of xmrecvlist running if the download is still in progress.

Q11. How can I tell if xmrecvlist is NOT working properly?

Note: xmrecvlist is being phased out; we recommend that you reset your browser to use DaRT; see the instructions for first-time users for details about doing this. DaRT is better at handling errors.

Usually one of the following will happen:

  1. A file-chooser window pops up.
  2. A short file listing the requested datasets is printed in the browser window.
  3. An error message appears in a pop-up window.

Symptoms 1. and 2. usually mean that your browser is not properly configured for use with the archive. See the instructions for first-time users to correct this. Symptom 3 is usually due to an error on the server; this sometimes happens when there is a large demand for data; however, see Q12 for details.

Q12. When I try to use the "button" multi-file retrieval method I get strange error messages in pop-up windows. What do they mean?

First, it probably means that you are using xmrecvlist (see Q7). We strongly encourage you to upgrade to DaRT as it is much better at dealing with error conditions; see the instructions for first-time users to learn how to upgrade.

In the meantime, here are a few error messages produced by xmrecvlist and what they mean:

Q13. Where can I find the latest supported version of xmrecvlist?

Note: xmrecvlist is being phased out; we recommend that you reset your browser to use DaRT; see the instructions for first-time users for details about doing this.

Normally, archive users just use the version of xmrecvlist that comes with the standard Miriad distribution. However, when this is not available or the version that is currently installed is out of date, the last supported version of xmrecvlist can be obtained available via anonymous ftp from atlas.ncsa.uiuc.edu in /pub/xmrecvlist.

NCSA BIMA Data Archive Quick Search Contact Archivist
The BIMA Data Archive is a project of Radio Astronomy Imaging Team
at the National Center for Supercomputing Applications on the campus of the University of Illinois at Urbana-Champaign

Contact the Archivist: bimadata@ncsa.uiuc.edu