19. UNIX Disk Handling

19.1 UNIX Disk Handling Utility

The UNIX operating system does not have the ability to link disk packs together under one user code. A utility, using the environment variable DATAPATH and a soft link, has been implemented in LAS to handle the situation when a particular user needs room on more than one disk. It physically places images on the disks named in DATAPATH and links them to the working directory by a soft link.

This utility also keeps track of the physical space on the disk so that two images being created at the same time do not allocate the same disk area. One of the "creates" will reserve the disk space and the other will be forced to utilize DATAPATH or to wait for disk space to become available. Below is the syntax for setting up DATAPATH:

     setenv DATAPATH "/edc/production/lams:/edc/production3/lams"
where the colon is used to separate each of directories.

NOTES:

  1. This applies to all large files.
  2. The account specified in DATAPATH must exist.
  3. A best fit algorithm is used to determine which disk to use for a particular image.
  4. UNIX operating system commands must not be used when working with these files.
For example, if the "remove" (rm) command is used to remove one of these files, the soft link will be deleted but the physical file is not deleted. Always use the cmdel function to remove files.