Technical data

Tuning Techniques
2.1 Subsystem Attributes
2.1.2 Modifying Subsystem Attribute Values
You can modify the values of subsystem attributes either temporarily or
permanently.
If you change the value of a subsystem attribute at run time, the change will
persist only as long as the system continues to run. When you reboot the system,
the attribute value reverts to the previous setting.
For temporary modifications that will not persist across reboots, use the
sysconfig -r command as described in Section 2.1.2.1.
To modify an attribute value permanently, include the attribute in the system
configuration table,
sysconfigtab . Values specified in sysconfigtab are
preserved through system reboots. To include an attribute in the sysconfigtab
file, use the sysconfigdb utility, as described in Section 2.1.3.
Note
Always use the recommended utility to modify subsystem attributes. Do
not modify the sysconfigtab file directly.
2.1.2.1 Reconfiguring Attributes
You can reconfigure an attribute (that is, modify its value temporarily), using
the sysconfig command, if the attribute is reconfigurable (the op code includes
R). This allows you to determine whether modifying an attribute will improve
your system performance. Temporary modifications are lost when you reboot the
system.
To temporarily modify an attribute’s current value, use the
sysconfig command
with the -r option. Specify both the subsystem and the attribute on the command
line:
For example, to modify the tcp_keepinit value to be 30 temporarily, enter the
following command:
TCPIP> sysconfig -r inet tcp_keepinit=30
tcp_keepinit: reconfigured
TCPIP>
After modifying the attribute value, you must either reload the subsystem or
restart TCP/IP Services, depending on whether the attribute is part of a dynamic
subsystem or a static subsystem.
• Unload the dynamic subsystem using the sysconfig -u command. Then use
the sysconfig -r command to reload the subsystem.
• Reload static subsystems by stopping and restarting TCP/IP Services.
2.1.3 Configuring Attributes
You can configure an attribute (that is, modify subsystem attributes so that
changes persist across reboots), by storing the attribute and its value in the
system configuration table (TCPIP$ETC:SYSCONFIGTAB.DAT), if the attribute’s
op code includes C.
When a subsystem is loaded, the attributes that are not listed in the
SYSCONFIGTAB.DAT file are set to their default values.
2–4 Tuning Techniques