NAME
nclist — number of cblocks for pty and tty data transfers
VALUES
Allowed Values
Minimum
132.
Maximum limited by available memory.
DESCRIPTION
nclist
specifies how many
cblocks
are allocated in the system.
Data traffic is stored in
cblocks
as it passes through tty and pty devices.
The default value for
nclist,
8292,
is based on a formula of 100
cblocks
for system use in handling traffic to the console, etc., plus an average of 16
cblocks
per user session, assuming 512 user sessions.
cblocks
are also used for serial connections other than login
sessions, such as as SLIP connections, UUCP transfers, terminal
emulators, and such.
If your system is using these other kinds of
connections,
nclist
should be increased accordingly.
If the
cblock
pool is exhausted, data being passed through a tty or
pty device might be lost because a
cblock
was not available when it was needed.
If this occurs, the warning message "cblock exhaustion has occurred n
times (see
termio(7))
is placed in the system message buffer.
Who Is Expected to Change This Tunable?
Users with the
SYSATTR
privilege.
See
privileges(5)
for more information about privileged access on systems that support
fine-grained privileges.
Restrictions on Changing
Changes to this tunable take effect at the next reboot.
When Should the Value of This Tunable Be Raised?
The tunable value can be increased in the following instances:
When the kernel sends the error message
WARNING: cblock exhaustion has occurred n times (see termio(7)).,
the system is running out of
cblocks.
This indicates that
nclist
needs to be increased.
The system may run slow for terminal I/O resulting in some data loss,
without displaying a warning message.
Increasing the
nclist
value may solve this problem.
The minimum value for
nclist
is
132.
There is no maximum, but each
cblock
consumes 32 bytes of resident (non-swappable) machine memory, so the
value should be selected with this in mind.
What Are the Side Effects of Raising the Value of This Tunable?
More resident (non-swappable) machine memory is used.
When Should the Value of This Tunable Be Lowered?
This value should be lowered when a minimal system is being created.
What Are the Side Effects of Lowering the Value of This Tunable?
The system may run out of
cblocks.
What Other Tunables Should Be Changed at the Same Time?
None.
WARNINGS
All HP-UX kernel tunable parameters are release specific.
This parameter may be removed or have its meaning changed in
future releases of HP-UX.
Installation of optional kernel software, from HP or other vendors,
may cause changes to tunable parameter values. After installation,
some tunable parameters may no longer be at the default or
recommended values. For information about the effects of
installation on tunable values, consult the documentation
for the kernel software being installed.
For information about optional kernel software that was
factory installed on your system, see
HP-UX Release Notes
at
http://docs.hp.com.
AUTHOR
nclist
was developed by HP.
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