scroll_lines.5 (2010 09)

s
scroll_lines(5) scroll_lines(5)
(Tunable Kernel Parameters)
NAME
scroll_lines - number of scrollable lines used by the Internal Terminal Emulator
VALUES
Failsafe
100
Default
100
Allowed values
60 to 999
Recommended values
No larger than is sufficient for a user’s purposes.
DESCRIPTION
This tunable specifies the total number of scroll buffer lines used by the HP-UX graphics console Internal
Terminal Emulator (ITE). This value is the sum of both on-screen and off-screen lines. For instance, if
the ITE has 68 on-screen lines, and the value of scroll_lines is 128, then there will be 60 off-screen lines
that can be scrolled back into view.
During boot, the system may adjust the value of scroll_lines upward, depending upon the installed
graphics hardware. On graphics cards capable of running at more than one resolution, the ITE will first
determine the maximum number of on-screen lines across all possible resolutions. The ITE will then
ensure that scroll_lines is at least equal to this number of on-screen lines. For example, assume the
graphics card supports two possible resolutions which result in one ITE resolution of 160 characters by 62
lines and another ITE resolution of 120 characters by 78 lines. If a value of 62 had been specified for
scroll_lines in the system file, the ITE would then adjust this value upwards to 78.
Who Is Expected to Change This Tunable?
Anyone.
Restrictions on Changing
Changes to this tunable take effect at the next reboot.
When Should the Value of This Tunable Be Raised?
The value of
scroll_line can be increased if the user would like to retain additional lines in the scroll
buffer.
What Are the Side Effects of Raising the Value of This Tunable?
Increasing the size of the ITE scroll buffer consumes kernel memory which will be dedicated to the ITE
and cannot be used for other purposes by the rest of the system. Memory is used at the rate of 2 bytes per
off-screen character.
When Should the Value of This Tunable Be Lowered?
If the additional off-screen lines in the scroll buffer are not required,
scroll_lines can be decreased
to free up a small amount of memory. The savings will be two bytes per off-screen character. For
instance, if the display is 160 characters wide, decreasing scroll_lines by 10 will free up 3200 bytes.
What Are the Side Effects of Lowering the Value of This Tunable?
If
scroll_lines is set below or equal to the number of lines displayed on the ITE screen, no off-screen
text will be accessible.
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 parame-
ter 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
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1