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      STACKER NOTE                                         STACKER NOTE
               CHECK I/O ACCESS DENIED ERROR 27 (STACKER 4.0)
                          (Applies to Stacker 4.0)
      STAC FAX  4706 (08-16-1994)
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      BACKGROUND
      
      If you receive this error while checking your Stacker drives, you
      may have corrupt data in the File Allocation Table (FAT). The
      errors could be caused by:
       - Bad sectors on the underlying physical drive
       - An errant program that writes data incorrectly and destroys
         part of the File Allocation Table (FAT)
       - A program that incorrectly uses Expanded Memory Specification
         (EMS)
        
      SOLUTION
      
      To correct this error:
       - Determine which areas of your hard drive have been damaged
       - Correct the damaged, unreadable areas
        
      Determine which areas of your hard drive have been damaged
      
      The first step is to clean boot your system and remove the
      hidden, system, and read-only attributes from the STACVOL file.
      Determine whether Stacker is preloading before CONFIG.SYS. If you
      are not sure, open the CONFIG.SYS file by typing ED /C <enter>.
      Look for the Stacker lines in the file. If one of them is similar
      to the line below, then Stacker does NOT preload:
      
           DEVICE=C:\STACKER\STACKER.COM
      If you do not see a STACKER.COM statement, and you have access to
      your Stacker drives, then your Stacker version is preloading.
      Select the appropriate procedure below.
      
      IF STACKER PRELOADS
      
       1.  From the DOS prompt type: STACKER <enter>.
       2.  Examine the drive map that is displayed and locate the
           damaged drive. The line will look something like this:
           Drive C was drive C at boot time [D:\STACVOL.DSK = 123.4MB]
           Note the drive letter and file name in brackets. In this
           case it is D:\STACVOL.DSK. This drive letter is the
           uncompressed boot drive.
       3.  Restart your system. Press the F5 key when you see the
           message "Starting xx-DOS...".
       4.  From the prompt, type:
           ATTRIB -H -R -S drive:\STACVOL.xxx <Enter>
           where drive:\STACVOL.xxx is the drive and file name you
           noted in step 2. In this example it is D:\STACVOL.DSK.
       5.  Change to the STACKER directory. Type STACKER -drive:
           <enter>, where drive: is the letter of your Stacker drive.
           In this example it is C.
           
       IF STACKER DOES NOT PRELOAD
           
       1.  From the DOS prompt type: STACKER <enter>.
       2.  Examine the drive map that is displayed and locate the
           damaged drive. The line will look something like this:
           Drive C was drive D at boot time [D:\STACVOL.DSK = 123.4MB]
           Note the drive letter and file name in brackets. In this
           case it is D:\STACVOL.DSK. This drive letter is the
           uncompressed boot drive.
       3.  Change to the DOS directory of the drive you noted above.
           Copy ATTRIB.EXE from the DOS directory of drive C to the DOS
           directory of the uncompressed boot drive.
       4.  Restart the computer using a system disk in drive A. Your
           Stacker drives will not be mounted.
       5.  Change to the DOS directory on drive C.
       6.  From the prompt, type:
           ATTRIB -H -R -S drive:\STACVOL.xxx <Enter>
           where drive:  is the drive where CHECK originally
           reported the error.
           
      Correct the damaged, unreadable areas
      
      Standard disk repair utilities such as Norton Utilities
      Calibrate, PC Tools DiskFix, or SpinRite, can detect the damaged
      areas and correct them. Run your disk repair utility from the
      floppy disk drive. This ensures that you are running an
      uncorrupted version of the utility. Also, if you do a clean boot,
      the utility may not be available from your hard disk.
      
      1. Run the disk repair utility on the damaged drive. This is the
         drive letter you used when running the ATTRIB command in the
         previous procedure. Ensure you run a vigorous test,
         preferrably at least a 40 pattern test. This may take a few
         hours. Allow it to repair any defective areas on the disk.
      2. Remove all disks from the floppy drives and restart the
         computer.
      3. Run the Stacker command CHECK /F.
         
      If there are no errors, the drive is repaired, and you can resume
         normal use of the drive.
         
      IF YOU STILL HAVE ERRORS
      
      If you still cannot repair the Stacker drive, there are three
      additional procedures you can try before resorting to removing
      the damaged drive and starting over:  removing write protection,
      removing the /EMS parameter, and restoring a backup copy if the
      STACVOL file header.
      
      Removing write protection
      
      To remove write protection, follow the procedure below, where
      "x:" indicates the drive letter of the compressed drive:
      Type:
              CHECK /=w x: <ENTER>
      Warning:  This command produces a message stating that the read-
      only status of this drive has been cleared.  Do not interpret
      this to mean that you can resume normal use of the drive; doing
      so prematurely will result in data loss.  Instead, you must
      complete the steps outlined below.  Never use CHECK /=W to remedy
      other write-protect situations.
      
      Run CHECK /F again. Follow the instructions to repair the drive.
      When prompted to perform a disk surface test, respond "yes," and
      delete the damaged files.
      
      When CHECK reports no more errors, the drive should be fully
      repaired. If errors persist, remove the /EMS parameter in the
      STACKER.INI file.
      
      Removing the /EMS parameter
      
      Persistent errors indicate that the drive's FAT is damaged.  Some
      programs use expanded memory improperly.  A program's
      undisciplined use of the EMS page frame can corrupt the FAT.  If
      this is the case, you can prevent further corruption by disabling
      Stacker's use of EMS memory.
      
       1. Type ED /I <enter>.
       2. Look for a line like this: /EMS
       3. Delete the line, press CTRL-Z to save the file and exit.
       4. Restart your system, then type CHECK /F to complete repairs.
           
      If errors persist, try restoring a backup copy of the header of
      the STACVOL file.
      
      Restore a backup copy of the STACVOL file header
      
      If the backup copy of the STACVOL  file header is error free,
      restoring it may correct problems in the drive's FAT.
      
       1.  Remove the attributes from the STACVOL file just as you did
           in the first procedure.
       2.  Change to the STACKER directory on the uncompressed drive
           and type:
           REPAIR /F drive:\STACVOL.xxx
           where drive:\STACVOL.xxx is the path and filename you typed
           when removing the STACVOL files attributes.
       3.  Allow the REPAIR utility to replace the STACVOL file header.
       4.  Restart the system and run CHECK /F to see if the damage was
           repaired.
      If errors persist, the drive's FAT may be damaged beyond repair.
      The only solution is to delete the drive with the damaged FAT and
      start over.
      
      Deleting the damaged drive and starting over
      
       1.  Back up the data on the drive.
       2.  Run the Stacker command REMOVDRV drive: to delete the
           damaged drive.
       3.  Restart the computer.
       4.  Compress the drive again and restore from backup.
           
      
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      Copyright 1994 Stac Electronics
