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  man pages->Tru64 Unix man pages -> mc (7)              



NAME    [Toc]    [Back]

       mc - SCSI medium changer interface

DESCRIPTION    [Toc]    [Back]

       The  medium  changer  (mc)  interface provides a means for
       applications to control the robotic medium changers  found
       in tape and optical libraries or jukeboxes.

       The mc driver may be used for any supported Small Computer
       System Interface (SCSI) medium changer devices, and potentially
 for other SCSI-compliant changer devices.  Applications
 use Unix I/O calls (open, close,  ioctl)  to  access
       changer   devices,  by  means  of  device  special  files.
       Changer device special files are typically created in  the
       /dev/changer  directory  by  the  dsfmgr utility on system
       startup.  Refer to the dsfmgr(8) Reference Page and System
       Administration  if  you  need  to  recreate device special
       files that are deleted accidentally. The rz(7)  and  tz(7)
       Reference  Pages  provide  information on how device names
       map to SCSI CAM lun addresses.

       The format of a a medium changer device special file  name


       where  N  is  an  integer representing the instance of the
       device that is assigned by dsfmgr at system startup.

       The driver supports a number of ioctl commands  that  move
       media  in  the  library  or  return  information about the
       media.         See         the         header         file
       /usr/sys/include/io/cam/mchanger.h  for the ioctl commands
       and their associated structs.

       An application opens the device special file corresponding
       to  the  changer  device,  executes appropriate ioctl commands,
 then closes the device  special  file.   Typically,
       changer  devices  are not shared between applications, but
       this is not due to any limitation on  the  changer  or  mc
       driver,  but  rather to the possibility of confusing which
       media belong to which application.  An  application  on  a
       non-cluster  system  can  assure  that  only  it can use a
       changer by opening that changer's device special file  for
       exclusive access, by including the O_EXCL flag in the open
       call, and leaving the file open until the  application  is
       completely  done  using  the  changer.   However,  if  the
       changer is on a shared bus in a cluster,  it  is  possible
       for  an  application  on  each  cluster member to open the
       device, even if each specifies O_EXCL, because  that  only
       grants  exclusive  access on the local host.  In this case
       it may be useful for the application to use a SCSI  device
       reservation to assure exclusive access.  (An ioctl command
       is provided to facilitate reserving a changer.)

       Refer to the Software Product Description for  a  list  of
       supported  devices  under  the heading of SCSI CAM Layered
       Components. Facilities are provided in the operating  system
 to allow the addition of some third-party SCSI-compliant
 medium changers.  Under Digital Unix V4.0  and  later,
       refer  to  the  ddr_config(8)  and  ddr.dbase(4) reference
       pages for  instructions.  Under  Digital  Unix  V3.x,  new
       devices  can  be  added  to /sys/data/cam_data.c. See that
       file for instructions.

FILES    [Toc]    [Back]

       changer device special file header file for changer  ioctl

SEE ALSO    [Toc]    [Back]

       Commands: mcutil(1), mcicap(4), dsfmgr(8), scu(8), uerf(8)

       Interfaces: op(7), tz(7), SCSI(7)

[ Back ]
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