VMS Help
V73 Features, System Management Features, New System Parameters
*Conan The Librarian (sorry for the slow response - running on an old VAX)
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This section contains definitions of system parameters that are
new in OpenVMS Version 7.3.
AUTO_DLIGHT_SAV is set to either 1 or 0. The default is 0.
If AUTO_DLIGHT_SAV is set to 1, OpenVMS automatically makes the
change to and from daylight saving time.
FAST_PATH_PORTS is a static parameter that deactivates Fast Path
for specific drivers.
FAST_PATH_PORTS is a 32-bit mask. If the value of a bit in the
mask is 1, Fast Path is disabled for the driver corresponding to
that bit. A value of -1 specifies that Fast Path is disabled for
all drivers that the FAST_PATH_PORTS parameter controls.
Bit position zero controls Fast Path for PKQDRIVER (for parallel
SCSI), and bit position one controls Fast Path for FGEDRIVER
(for Fibre Channel). Currently, the default setting for FAST_
PATH_PORTS is 0, which means that Fast Path is enabled for both
PKQDRIVER and FGEDRIVER.
In addition, note the following:
o CI drivers are not controlled by FAST_PATH_PORTS. Fast Path
for CI is enabled and disabled exclusively by the FAST_PATH
system parameter.
o FAST_PATH_PORTS is relevant only if the FAST_PATH system
parameter is enabled (equal to 1). Setting FAST_PATH to zero
has the same effect as setting FAST_PATH_PORTS to -1.
For additional information, see FAST_PATH and IO_PREFER_CPUS.
On Galaxy systems, GLX_SHM_REG is the number of shared memory
region structures configured into the Galaxy Management Database
(GMDB). If you set GLX_SHM_REG to 0, the default number of shared
memory regions are configured.
The LCKMGR_CPUID parameter controls the CPU that the Dedicated
CPU Lock Manager runs on. This is the CPU that the LCKMGR_SERVER
process will utilize if you turn this feature on with the LCKMGR_
MODE system parameter.
If the specified CPU ID is either the primary CPU or a
nonexistent CPU, the LCKMGR_SERVER process will utilize the
lowest nonprimary CPU.
LCKMGR_CPUID is a DYNAMIC parameter.
For more information, see the LCKMGR_MODE system parameter.
The LCKMGR_MODE parameter controls usage of the Dedicated CPU
Lock Manager. Setting LCKMGR_MODE to a number greater than zero
(0) indicates the number of CPUs that must be active before the
Dedicated CPU Lock Manager is turned on.
The Dedicated CPU Lock Manager performs all locking operations
on a single dedicated CPU. This can improve system performance
on large SMP systems with high MP_Synch associated with the lock
manager.
For more information about usage of the Dedicated CPU Lock
Manager, see the OpenVMS Performance Management manual.
Specify one of the following:
Value Description
0 Indicates the Dedicated CPU Lock Manager is off. (The
default.)
>0 Indicates the number of CPUs that must be active before
the Dedicated CPU Lock Manager is turned on.
LCKMGR_MODE is a DYNAMIC parameter.
NPAGECALC controls whether the system automatically calculates
the initial size for nonpaged dynamic memory.
Compaq sets the default value of NPAGECALC to 1 only during the
initial boot after an installation or upgrade. When the value of
NPAGECALC is 1, the system calculates an initial value for the
NPAGEVIR and NPAGEDYN system parameters. This calculated value is
based on the amount of physical memory in the system.
NPAGECALC's calculations do not reduce the values of NPAGEVIR and
NPAGEDYN from the values you see or set at the SYSBOOT prompt.
However, NPAGECALC's calculation might increase these values.
AUTOGEN sets NPAGECALC to 0. NPAGECALC should always remain 0
after AUTOGEN has determined more refined values for the NPAGEDYN
and NPAGEVIR system parameters.
NPAGERAD specifies the total number of bytes of nonpaged pool
that will be allocated for Resource Affinity Domains (RADs) other
than the base RAD. For platforms that have no RADs, NPAGERAD
is ignored. Notice that NPAGEDYN specifies the total amount of
nonpaged pool for all RADs.
Also notice that the OpenVMS system might round the specified
values higher to an even number of pages for each RAD, which
prevents the base RAD from having too little nonpaged pool. For
example, if the hardware is an AlphaServer GS160 with 4 RADs:
NPAGEDYN = 6291456 bytes
NPAGERAD = 2097152 bytes
In this case, the OpenVMS system allocates a total of
approximately 6,291,456 bytes of nonpaged pool. Of this amount,
the system divides 2,097,152 bytes among the RADs that are not
the base RAD. The system then assigns the remaining 4,194,304
bytes to the base RAD.
RAD_SUPPORT enables RAD-aware code to be executed on systems
that support Resource Affinity Domains (RADs); for example,
AlphaServer GS160 systems.
A RAD is a set of hardware components (CPUs, memory, and I/O)
with common access characteristics. For more information
about using OpenVMS RAD features, refer to the OpenVMS Alpha
Partitioning and Galaxy Guide.
SHADOW_MAX_UNIT specifies the maximum number of shadow sets that
can exist on a node. The setting must be equal to or greater
than the number of shadow sets you plan to have on a system.
Dismounted shadow sets, unused shadow sets, and shadow sets with
no write bitmaps allocated to them are included in the total.
This system parameter is not dynamic; that is, a reboot is
required when you change the setting.
The default setting on OpenVMS Alpha systems is 500; on OpenVMS
VAX systems, the default is 100. The minimum value is 10, and the
maximum value is 10,000.
Note that this parameter does not affect the naming of shadow
sets. For example, with the default value of 100, a device name
such as DSA999 is still valid.
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10 - VCC MAX IO SIZE (Alpha)
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The dynamic system parameter VCC_MAX_IO_SIZE controls the maximum
size of I/O that can be cached by the Extended File Cache. It
specifies the size in blocks. By default, the size is 127 blocks.
Changing the value of VCC_MAX_IO_SIZE affects reads and writes to
volumes currently mounted on the local node, as well as reads and
writes to volumes mounted in the future.
If VCC_MAX_IO_SIZE is 0, the Extended File Cache on the local
node cannot cache any reads or writes. However, the system is
not prevented from reserving memory for the Extended File Cache
during startup if a VCC$MIN_CACHE_SIZE entry is in the reserved
memory registry.
VCC_MAX_IO_SIZE is a DYNAMIC parameter.
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11 - VCC READAHEAD (Alpha)
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The dynamic system parameter VCC_READAHEAD controls whether
the Extended File Cache can use read-ahead caching. Read-
ahead caching is a technique that improves the performance of
applications that read data sequentially.
By default VCC_READAHEAD is 1, which means that the Extended File
Cache can use read-ahead caching. The Extended File Cache detects
when a file is being read sequentially in equal-sized I/Os, and
fetches data ahead of the current read, so that the next read
instruction can be satisfied from cache.
To stop the Extended File Cache from using read-ahead caching,
set VCC_READAHEAD to 0.
Changing the value of VCC_READAHEAD affects volumes currently
mounted on the local node, as well as volumes mounted in the
future.
Readahead I/Os are totally asynchronous from user I/Os and only
take place if sufficient system resources are available.
VCC_READAHEAD is a DYNAMIC parameter.
WBM_MSG_INT is one of three system parameters that are available
for managing the update traffic between a master write bitmap
and its corresponding local write bitmaps in an OpenVMS Cluster
system. (Write bitmaps are used by the volume shadowing software
for minicopy operations.) The others are WBM_MSG_UPPER and
WBM_MSG_LOWER. These parameters set the interval at which the
frequency of sending messages is tested and also set an upper and
lower threshold that determine whether the messages are grouped
into one SCS message or are sent one by one.
In single-message mode, WBM_MSG_INT is the time interval in
milliseconds between assessments of the most suitable write
bitmap message mode. In single-message mode, the writes issued by
each remote node are, by default, sent one by one in individual
SCS messages to the node with the master write bitmap. If the
writes sent by a remote node reach an upper threshold of messages
during a specified interval, single-message mode switches to
buffered-message mode.
In buffered-message mode, WBM_MSG_INT is the maximum time a
message waits before it is sent. In buffered-message mode, the
messages are collected for a specified interval and then sent
in one SCS message. During periods of increased message traffic,
grouping multiple messages to send in one SCS message to the
master write bitmap is generally more efficient than sending each
message separately.
The minimum value of WBM_MSG_INT is 10 milliseconds. The maximum
value is -1, which corresponds to the maximum positive value that
a longword can represent. The default is 10 milliseconds.
WBM_MSG_INT is a DYNAMIC parameter.
WBM_MSG_LOWER is one of three system parameters that are
available for managing the update traffic between a master write
bitmap and its corresponding local write bitmaps in an OpenVMS
Cluster system. (Write bitmaps are used by the volume shadowing
software for minicopy operations.) The others are WBM_MSG_INT
and WBM_MSG_UPPER. These parameters set the interval at which the
frequency of sending messages is tested and also set an upper and
lower threshold that determine whether the messages are grouped
into one SCS message or are sent one by one.
WBM_MSG_LOWER is the lower threshold for the number of messages
sent during the test interval that initiates single-message mode.
In single-message mode, the writes issued by each remote node
are, by default, sent one by one in individual SCS messages
to the node with the master write bitmap. If the writes sent
by a remote node reach an upper threshold of messages during a
specified interval, single-message mode switches to buffered-
message mode.
The minimum value of WBM_MSG_LOWER is 0 messages per interval.
The maximum value is -1, which corresponds to the maximum
positive value that a longword can represent. The default is
10.
WBM_MSG_LOWER is a DYNAMIC parameter.
WBM_MSG_UPPER is one of three system parameters that are
available for managing the update traffic between a master write
bitmap and its corresponding local write bitmaps in an OpenVMS
Cluster system. (Write bitmaps are used by the volume shadowing
software for minicopy operations.) The others are WBM_MSG_INT
and WBM_MSG_LOWER. These parameters set the interval at which the
frequency of sending messages is tested and also set an upper and
lower threshold that determine whether the messages are grouped
into one SCS message or are sent one by one.
WBM_MSG_UPPER is the upper threshold for the number of messages
sent during the test interval that initiates buffered-message
mode. In buffered-message mode, the messages are collected for a
specified interval and then sent in one SCS message.
The minimum value of WBM_MSG_UPPER is 0 messages per interval.
The maximum value is -1, which corresponds to the maximum
positive value that a longword can represent. The default is
100.
WBM_MSG_UPPER is a DYNAMIC parameter.
WBM_OPCOM_LVL controls whether write bitmap system messages are
sent to the operator console. (Write bitmaps are used by the
volume shadowing software for minicopy operations.) Possible
values are shown in the following table:
Value Description
0 Messages are turned off.
1 The default; messages are provided when write bitmaps are
started, deleted, and renamed, and when the SCS message
mode (buffered or single) changes.
2 All messages for a setting of 1 are provided plus many
more.
WBM_OPCOM_LVL is a DYNAMIC parameter.
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