SYNCSTAT(8) Maintenance Procedures SYNCSTAT(8)


syncstat - report driver statistics from a synchronous serial link


/usr/sbin/syncstat [-c] device [interval]


The syncstat command reports the event statistics maintained by a
synchronous serial device driver. The report may be a single snapshot of
the accumulated totals, or a series of samples showing incremental
changes. Prior to these it prints the device name being used to query a
particular device driver, along with a number indicating the channel
number (ppa) under control of that driver.

Event statistics are maintained by a driver for each physical channel
that it supports. They are initialized to zero at the time the driver
module is loaded into the system, which may be either at boot time or
when one of the driver's entry points is first called.

The device argument is the name of the serial device as it appears in
the /dev directory. For example, zsh0 specifies the first on-board
serial device.

The following is a breakdown of syncstat output:

speed The line speed the device has been set
to operate at. It is the user's
responsibility to make this value
correspond to the modem clocking speed
when clocking is provided by the
ipkts The total number of input packets.
opkts The total number of output packets.
undrun The number of transmitter underrun
ovrrun The number of receiver overrun errors.
abort The number of aborted received frames.
crc The number of received frames with CRC
isize The average size (in bytes) of input
osize The average size (in bytes) of output


Clear the accumulated statistics for the device specified.
This may be useful when it is not desirable to unload a
particular driver, or when the driver is not capable of being

syncstat samples the statistics every interval seconds and
reports incremental changes. The output reports line
utilization for input and output in place of average packet
sizes. These are the relationships between bytes transferred
and the baud rate, expressed as percentages. The loop repeats
indefinitely, with a column heading printed every twenty
lines for convenience.


Example 1: Sample output from the syncstat command:

example# syncstat zsh0

speed ipkts opkts undrun ovrrun abort crc isize osize
9600 15716 17121 0 0 1 3 98 89

example# syncstat -c zsh0

speed ipkts opkts undrun ovrrun abort crc isize osize
9600 0 0 0 0 0 0 0 0

In the following sample output a new line of output is generated every
five seconds:

example# syncstat zsh0 5

ipkts opkts undrun ovrrun abort crc iutil outil
12 10 0 0 0 0 5% 4%
22 60 0 0 0 0 3% 90%
36 14 0 0 0 1 51% 2%


zsh(4D), attributes(7), syncinit(8), syncloop(8)


bad interval: arg

The argument arg is expected to be an interval and could not be

device missing minor device number

The name device does not end in a decimal number that can be used as
a minor device number.

baud rate not set

The interval option is being used and the baud rate on the device is
zero. This would cause a divide-by-zero error when computing the line
utilization statistics.


Underrun, overrun, frame-abort, and CRC errors have a variety of causes.
Communication protocols are typically able to handle such errors and
initiate recovery of the transmission in which the error occurred. Small
numbers of such errors are not a significant problem for most protocols.
However, because the overhead involved in recovering from a link error
can be much greater than that of normal operation, high error rates can
greatly degrade overall link throughput. High error rates are often
caused by problems in the link hardware, such as cables, connectors,
interface electronics or telephone lines. They may also be related to
excessive load on the link or the supporting system.

The percentages for input and output line utilization reported when using
the interval option may occasionally be reported as slightly greater than
100% because of inexact sampling times and differences in the accuracy
between the system clock and the modem clock. If the percentage of use
greatly exceeds 100%, or never exceeds 50%, then the baud rate set for
the device probably does not reflect the speed of the modem.

March 9, 1993 SYNCSTAT(8)