Technical data

Tuning Techniques
2.2 Tuning Server Applications
Table 2–5 (Cont.) net Subsystem Attributes
Attribute Description
ovms_unit_creates Information attribute that shows a running total of all the
BG devices created since TCP/IP Services was started. You
can use this information to see how often devices are being
used. You cannot modify this attribute.
ovms_unit_fast_credel Specifies fast creation and deletion of BG devices, useful
on a system that uses many BG devices. Modifying this
attribute can improve performance by reducing:
• The impact of the device list scan on the CPU cache.
• The time that the I/O mutex is held for write access
during the SYS$ASSIGN( ) and SYS$DASSGN( )
system services.
The default setting for this attribute is 0, or OFF.
This attribute can affect the amount of virtual memory
used. To calculate the effect of this attribute on virtual
memory usage, add one to the the number of BG devices
(
ovms_unit_maximum ) and multiply by 4. For example,
with the default setting of 9999, the virtual memory is
40,000 bytes. At its maximum value of 32767, the virtual
memory is 131,072 bytes.
You can modify this attribute.
ovms_unit_limit
This informational attribute shows the calculated maximum
number of concurrent BG device units that can coexist at
any time given the values of the
ovms_unit_maximum and
ovms_unit_minimum attributes. Note that BG0 and BG1
are always reserved. You cannot modify this attribute.
ovms_unit_minimum Specifies the lowest numbered device unit. All BG devices
after BG0 will begin with this unit number. You can modify
this attribute.
ovms_unit_maximum
Specifies the highest numbered device unit. It is possible
there will be BG device numbers above this, but they are
not available to users. You can specify a value from 9999 to
32767. You can modify this attribute.
ovms_unit_seed This informational attribute shows the next BG unit
number that will be created. If
ovms_unit_fast_credel
is enabled, a duplicate BG device unit is sensed
immediately and the unit seed incremented. If
ovms_unit_fast_credel is not enabled, a device scan
will occur as it normally does with cloned devices.
To modify ovms_unit_fast_credel , ovms_unit_minimum , and ovms_unit_maximum ,
define them in the SYSCONFIGTAB.DAT file, as described in Section 2.1.2.
2.3 Solving Performance Problems
This section contains information that you can use to identify and solve server
performance problems.
The following tasks can help you to solve performance problems:
• Monitor the server.
See Section 1.2.4 for information about monitoring the network, the virtual
memory subsystem, and network socket statistics.
Tuning Techniques 2–17