Everhart, Glenn
From:	Terry Kennedy [terry@spcunb.spc.edu]
Sent:	Wednesday, September 02, 1998 7:46 AM
To:	Info-VAX@Mvb.Saic.Com
Subject:	Re: Can I change Error count on a disk?
paddy.o'brien@zzz.tg.nsw.gov.au writes:
> I have searched the bookreader manuals and spoken to our systems contractors for 
> our corporate machines.  None /neither were able to remember a way to revert the 
> error count on a disk to zero.  I have never needed this before, but would like 
> to do it now, if possible without re-booting -- the only way that we could think 
> of.

  I remember something called "ZDEC" (I think) on a long-ago SIG tape. It may
appear on newer SIG tapes, and maybe even an Alpha version. At least the name
should give you something to search on.

  Also, here is a Bliss skeleton which claims to work on Alphas (from the
DECUServe system at telnet://eisner.decus.org):

                 <<< EISNER::$2$DIA7:[NOTES$HIVOL]VMS.NOTE;1 >>>
                         -< VMS and bundled utilities >-
================================================================================
Note 1650.9              Can the error count be zeroed?                   9 of 9
EISNER::WATSON_G "George Watson"                     46 lines  13-APR-1998 18:46
                -< Code to clear device error counts, Alpha V7 >-
--------------------------------------------------------------------------------
Here is a BLISS version that I have used successfully from Alpha VMS V7.1.  
This is the guts of the utility, the routine that you call via $CMKRNL.  You 
would want to wrap this in a main program that uses your preferred method of
getting the device name from the user, then doing the change mode.  Note that 
this uses the new *_STD$* routines, which use normal (i.e., easy to use from 
C) calls instead of JSBs.

LIBRARY 'SYS$LIBRARY:lib';
EXTERNAL ROUTINE
  LIB$get_foreign, LIB$put_output,
  SCH_STD$iolockw, SCH_STD$iounlock : NOVALUE, IOC_STD$searchdev;

ROUTINE zero_error_internal(devname : REF $BBLOCK) =
BEGIN
!***
! This is the kernal mode routine to clear the error count. The device name is
! passed by descriptor.
!***
  LOCAL
    sts, mutex_adr,
    ucb : REF $BBLOCK, ddb : REF $BBLOCK, sb : REF $BBLOCK;
  EXTERNAL CTL$GL_pcb : REF $BBLOCK;
!
!    Get the IO mutex for write.  This will set IPL to ASTDEL.
!
  mutex_adr = SCH_STD$iolockw(.CTL$GL_pcb);
!
!    Locate the device, and get its UCB.
!
  sts = IOC_STD$searchdev(.devname, ucb, ddb, sb);
  IF .sts THEN
    BEGIN
!
!    We found it.  Acquire the fork lock, which is used to serialize 
!    modifications to the UCB, and zero the count.
!
      $forklock(LOCK=.ucb[UCB$B_flck]); ucb[UCB$L_errcnt] = 0;
      $forkunlock(LOCK=.ucb[UCB$B_flck],NEWIPL=IPL$_astdel);
    END;
!
!    Unlock the IO mutex. We are left at mode of caller (ASTDEL), so lower
!    IPL afterwards.
!
  SCH_STD$iounlock(.CTL$GL_pcb); $enbint(SRC=0);
  .sts
END;

	Terry Kennedy		  Operations Manager, Academic Computing
	terry@spcvxa.spc.edu	  St. Peter's College, Jersey City, NJ USA
        +1 201 915 9381 (voice)   +1 201 435-3662 (FAX)