AIPS NRAO AIPS HELP file for VLBALOAD in 31DEC25



As of Mon Feb 17 11:13:59 2025


VLBALOAD: Procedure to load VLBA data from tape

INPUTS

INTAPE            0.0       9.0    Input tape drive number
DATAIN                             Disk file name
NFILES         -999.0    9999.0    # of files to advance on tape
NCOUNT            0.0    9999.0    Number of files to load
                                   (read from insert card)
OUTNAME                            Output file name
OUTDISK           0.0      15.0    Disk drive for output data
                                   (0 => any)
DOUVCOMP         -1.0       1.0    >0 => write compressed data
CLINT                              CL entry interval (min)
                                   0 => 0.25 minute
DOCONCAT         -1.0        1.0   >0 -> if VLBA correlator data
                                   append data to existing
                                   files, or if no appropriate
                                   files exist create a new file
                                   and append all data to that
                                   file.

          VLBALOAD is defined in the VLBAUTIL run file.

HELP SECTION

VLBALOAD
Type: Procedure
Use:  VLBALOAD is a procedure that loads VLBA data from tape and may
      be used for any data from the VLBA correlator.  VLBALOAD also
      runs TAMGR to merge redundant entries in the calibration tables
      (GC, TY and PC) (this makes running VLBAMCAL unnecessary).

      Type RUN VLBAUTIL to make the VLBALOAD procedure available.
      Note that VLBALOAD permanently flags data with weights less than
      0.7, which is fine for most data sets.

Adverbs:
  INTAPE......The input tape drive number. This procedure assumes that
              you have already mounted a FITS tape on this drive. Zero
              defaults to tape drive number one.
  DATAIN......48-character name of the disk file from which to read a
              FITS file.  It must be in the form
                  :
              or
                  :::
              where  is the remote computer name,  is the
              environment variable (logical name) for the disk area in
              which the file named  is stored.   is
              usually omitted when the file is local to the current
              computer.  If DATAIN is not found, the task will try
              DATAIN with the character 1 appended.
              Beginning 2003-Oct-16 FITLD can read more than one disk
              file at a time.  In that case, they must all have the
              same name except that the last letter(s) are the
              sequence number 1 through NCOUNT with no leading zeros.
              DATAIN must give the base name only, omitting the
              sequence number.  Then either
                    DATAIN = 'MYDATA:file_
              or
                    DATAIN = 'MYDATA:file_1
              can access files in $MYDATA named file_1, file_2,
              file_3, etc.  Note that this is similar to the pieces of
              a FITS pieced UV-table data set, but only one UV-table
              data set may be read at a time.
  NFILES......# of files to skip on tape before reading data.  For
              example, 1 => start of next file, -1 => start of previous
              file.  0 => no tape movement at all.  (AIPS verbs AVFILE
              plus TPHEAD allow you to position and check the tape in
              advance; be sure to reset NFILES to 0 for FITLD after
              them.)
  NCOUNT......The number of files to read from the tape.
              Zero defaults to a large number.
              You can read the number of files on a VLBA
              correlator tape from the listing inserted in the
              tape case.
  OUTNAME.....The name for the output files. The output files
              will all be given the class UVDATA and assigned
              distinct sequence numbers as needed.
  OUTDISK.....The disk drive number for the output data. Choose
              a disk with a large amount of space.
  DOUVCOMP....If true (> 0.5) then output data will be
              compressed which saves disk space at the expense
              of losing some weighting information.
  CLINT.......Calibration table interval in minutes. This should
              normally be in the range 0.25 to 1.0.  If <=0 then
              0.25 is assumed.
  DOCONCAT...If true (>0) and the input data are VLBA binary tables
             (IDI directly from the correlator) then data are to be
             appended to an existing file if possible.  Possible
             output files can be selected by OUTNAME, OUTDISK and
             OUTSEQ.  Use this option with CAUTION; it is REQUIRED (to
             be true) if you wish to concatenate the data from
             multiple files being read in the same execution of FITLD
             for VLBA correlator data.  (UV table pieces from FITAB
             are concatenated to each other even if DOCONCAT is false.)
             If DOCONCAT is false and OUTSEQ is specified, FITLD will
             fail at the start of file 2.  If DOCONCAT is false and
             OUTSEQ is not specified, then FITLD will make separate disk
             files for each tape file.  These disk files may be
             concatenated later with DBCON, but perhaps only after
             they have been MATCHed.  FITLD will write one or, if it
             finds data that do not match in e.g. number of channels,
             more output files.  If DOCONCAT is TRUE then FITLD will
             look over all files matching the OUTNAME, OUTCLAS,
             OUTSEQ, OUTDISK parameters to try to find one that it can
             append data to.  If it does not it will create one based
             on these name parameters.  That will generally fail if
             OUTSEQ is specified.  Thus, for DOCONCAT true, set
             OUTSEQ=0.  Be very careful if specifying ANTNAME with
             DOCONCAT true.

EXPLAIN SECTION

VLBALOAD:           Procedure to load VLBA data from tape.
Documentor:         Chris Flatters
Related Programs:   FITLD, VLBAUTIL, VLBAMCAL, TAMGR

WHEN TO USE VLBALOAD

Use VLBALOAD to load all of the data from one or more VLBA export tapes
into a single AIPS file. Do not use VLBALOAD if you need to apply data
selection criteria or otherwise need more control over FITLD.  As
VLBALOAD permanently flags data with weights less than 0.7, VLBALOAD is
not appropriate for data with a high fraction of low weights.  VLBALOAD
will also run TAMRG to merge redundant entries in the calibration tables
(GC, TY and PC).  This will only be run if there are calibration tables
and more than 1 file has been loaded from tape.  THIS IS A NEW FEATURE
AND MAKES RUNNING VLBAMCAL UNNECESSARY.

VLBALOAD is primarily intended for novice VLBA users and ensures that
FITLD is run with settings that make sense for most VLBA experiments.
It is also used in pipeline scripts.


LOADING DATA WITH VLBALOAD

1) If you have not already done so, type RUN VLBAUTIL to make the
   VLBALOAD procedure available to you.

2) Examine the listings inserted in each of your tapes and sum the total
   kilobytes for all of the tapes. This approximates the size of the
   uncompressed data set that will be used in AIPS.

3) Type FREE and check the free blocks for each disk. You will need
   enough disk space to hold at least 2 copies of your data in order to
   process it.

4) If there is at least one disk where the number of free blocks is more
   than twice the uncompressed size of your data in kilobytes or if
   there are at least two disks where the number of free blocks is
   greater than the uncompressed size of your data in kilobytes then set
   DOUVCOMP to FALSE, set OUTDISK to the number of a disk with a number
   of free blocks greater than the uncompressed size of your data, and
   then proceed to Step 7, otherwise continue with Step 5.

5) Divide the uncompressed size of your data by 3. This is a rough
   estimate of the compressed size of your data. If there is at least
   one disk where the number of free blocks is more than twice the
   compressed size of your data or if there are at least two disks
   where the number of free blocks is greater than the compressed size
   of your data then set DOUVCOMP to TRUE, set OUTDISK to the number of
   a disk with a number of free blocks greater than the uncompressed
   size of your data, and then proceed to Step 7, otherwise continue
   with Step 6.

6) If you have reached this point then you do not have sufficient disk
   space to reduce you data. You either need to delete some old files
   or to find a machine with more disk space.

7) Choose a calibration table interval and specify it as CLINT. One
   minute will be suitable for most experiment. Higher frequency bands
   may require shorter intervals. Consult a more experienced VLBA user
   if you are not sure what to use.

8) Specify a name for your output data files. The OBSCODE is often a
   good choice.

9) Specify the tape drive that you will be using as INTAPE.

10) Insert the first tape in your drive and mount it using the MOUNT
    verb.

11) In most cases set NFILES to 0

12) Set NCOUNT to the number of files listed on the insert and then type
    VLBALOAD.

13) When the procedure finishes and the AIPS prompt reappears, dismount
    the tape.

14) If you have more than one tape then repeat steps 10 through 12 for
    each remaining tape.

WHAT TO DO NEXT

After loading the data, you should normally run VLBAFIX to sort the
data etc, if necessary.

AIPS