Starting with OpenVMS Version 7.3, system parameters are available
for managing update traffic between a master write bitmap and its
corresponding local write bitmaps in an OpenVMS Cluster system.
Another system parameter controls whether write bitmap system messages
are sent to the operator console and, if they are to be sent, the
volume of messages. These system parameters are dynamic; that is,
they can be changed on a running system. They are shown in
Write Bitmap System Parameters and described in detail
in
System Parameters for Managing Write Bitmap Messages and Shadow Set Limit. These
system parameters support the minicopy operation (see
Using Minicopy for Backing Up Data (Alpha)).
In single-message
mode, the time interval between assessment of the most suitable
write bitmap message mode. In buffered-message mode, the maximum
time a message waits before it is sent.
msec
10
-1
10
WBM_MSG_UPPER
The upper threshold
for the number of messages sent during the test interval that will
initiate buffered-message mode.
msgs/interval
0
-1
100
WBM_MSG_LOWER
The lower threshold
for the number of messages sent during the test interval that will
initiate single-message mode.
msgs/interval
0
-1
10
WBM_OPCOM_LVL
Controls whether write bitmap
messages are provided to the operator console: 0 means messages are
turned off; 1 means messages are provided when write bitmaps are
started, deleted, and renamed, and when the SCS message mode (buffered
or single) changes; 2 means that all messages for a setting of 1 are
provided along with detailed messages for debugging purposes.
n/a
0
2
1
Setting System Parameters To
set or modify volume shadowing parameters, edit the [SYSn.SYSEXE]MODPARAMS.DAT file or the appropriate AUTOGEN
include file. After editing the file, execute SYS$UPDATE:AUTOGEN
as described in the HP OpenVMS System Manager's Manual, Volume 2: Tuning, Monitoring, and Complex Systems. If you have an OpenVMS Cluster system,
ensure that the system parameters are updated on each node. MODPARAMS.DAT File illustrates a MODPARAMS.DAT
file that includes assignment statements to set shadowing parameters.
Example 2 MODPARAMS.DAT File
.
.
.
! Volume Shadowing Parameters:
SHADOWING=2 ! Enables phase II shadowing
SHADOW_SYS_DISK=1 ! Enables system disk shadowing
SHADOW_SYS_UNIT=7 ! Specifies 7 as the virtual unit number
of the system disk
SHADOW_MAX_COPY=4 ! Specifies that 4 parallel copies can occur at one time
SHADOW_MBR_TMO=120 ! Allows 120 seconds for physical members to fail over
! before removal from the shadow set
.
.
.
See the HP OpenVMS System Manager's Manual, Volume 2: Tuning, Monitoring, and Complex Systems for complete information about invoking
AUTOGEN and specifying the appropriate command qualifiers to perform
the desired AUTOGEN operations.
Displaying System Parameters It
is sometimes useful to use the SYSGEN command SHOW to display the
values of system parameters. You do not need special privileges
to invoke the SYSGEN utility. You can use either a qualifier or
the name of a system parameter with the SHOW command, or you can
use the SHOW/ALL command to display information about all system
parameters. (Enter HELP SHOW at the SYSGEN> prompt for
more information about the SHOW command.) The following example
illustrates how you can check the current default, minimum, and maximum
values for the SHADOWING parameter.
$ MCR SYSGEN SYSGEN> SHOW SHADOWING Parameter Name Current Default Minimum Maximum Unit Dynamic -------------- ------- ------- ------- ------- ---- ------- SHADOWING 2 0 0 3 Coded-value SYSGEN>
HP Volume Shadowing for OpenVMS
Preparing to Use Volume Shadowing
