obsdata changes the directory in which the DAS writes observations.
The DAS uses a directory-naming convention in which the final sub-directory is the date on which the observing-night began. The sub-directory can be in one of a number of raw-data disks and obsdata selects the disk; the DAS adds the date to the directory name.
obsdata partitionwhere partition is the full path-name of the partition up to but not including the date.
obsdata /obsdata/intagiven at 1600hrs on 26th March 1997 selects the directory
/obsdata/inta/19970526
The DAS remembers the data-directory from night to night.
The directory change applies to all DAS channels that are active at the time. For INT WFC, all four channels write to the same directory.