NAME    [Toc]    [Back]

       vmzcore - compressed memory core dump interface

DESCRIPTION    [Toc]    [Back]

       The  vmzcore character special device file provides access
       to in-memory compressed kernel core dumps. During the boot
       sequence, savecore uses this device to recover an existing
       dump. (See the savecore(8) reference page for more  information.)


       An  application  can  determine  whether  a dump exists by
       opening and attempting to read a single byte from vmzcore;
       if  no  data  is  available,  no  dump  exists.  If a dump
       exists, the dump header can be read from byte offset  1024
       (2  *  DEV_BSIZE); upon reading the header, an application
       may treat vmzcore like a traditional swap device dump.   A
       dump  remains in memory until either an application writes
       to vmzcore or the memory system is powered down or  reset.

       By  default,  the system attempts a memory dump only after
       failing the initial disk dump.  The dump_to_memory  system
       attribute  changes this behavior.  If set to `1', the system
 attempts to save core dumps to memory then attempts to
       save  them  to  disk  if  the memory dump fails. If set to
       `-1', core dumps never are written to memory. The  default
       value is `0'.  (See sys_attrs_generic(5) for more information
 on system attributes.)

       This interface also supports a variation of  memory  dumps
       called  "exempt  memory  dumps".   A  contiguous  chunk of
       exempt memory is first reserved at  boot  time  using  the
       Contiguous Memory Allocator. (See sysconfigdb(8).)  A portion
 or all of this memory may then be handed to the  kernel
  dump  subsystem,  which will use it in the event of a
       memory core dump.  The  system  attribute  dump_exmem_addr
       identifies  the  start of the dumpable region (either as a
       virtual or physical address).  The dump_exmem_size  system
       attribute  specifies  the  number  of  bytes available. By
       default, exempt memory is not included in the  core  dump;
       this  can  be  changed  by  setting  the  system attribute
       dump_exmem_include to `1'.

RESTRICTIONS    [Toc]    [Back]

       Regarding   the   exempt   memory    system    attributes,
       dump_exmem_addr must be page aligned and dump_exmem_size a
       multiple of the machine word size (8  bytes).   When  combined,
  this  range of pages must be of type M_EXEMPT.  If
       any of these conditions are not met, the  system  displays
       an  error message and no exempt memory dump will be generated.


       Memory dumps must be compressed.  If  the  compressed_dump
       system attribute is not set, the system automatically will
       enable compression before attempting to write the dump.

FILES    [Toc]    [Back]

       /dev/vmzcore

SEE ALSO    [Toc]    [Back]

       Commands:  dxkerneltuner(8),  savecore(8),   sysconfig(8),
       sysconfigdb(8)

       Files: sys_attrs_generic(5) mem(7), kmem(7)

       Kernel Debugging, System Administration



                                                       vmzcore(7)