Cisco MDS 9000 Series Configuration Manual page 163

Congestion Detection, Avoidance, and Isolation
108369199104 2.5us TxWait due to lack of transmit credits
Percentage Tx credits not available for last 1s/1m/1h/72h: 0%/0%/0%/0%
32 receive B2B credit remaining
128 transmit B2B credit remaining
Last clearing of "show interface" counters: 6w 4d
2.5us TxWait due to lack of transmit credits – Count of TxWait ticks in 2.5us since
the interface counters have ben cleared last. In this example, 108369199104 * 2.5
/ 1000000 = 270922.99776 seconds of time the interface has not been able to transmit
in the past 6 weeks and 4 days.
Percentage Tx credits not available for last 1s/1m/1h/72h: 0%/0%/0%/0% - Percentage
of TxWait as calculated in the last 1 second, 1 minute, 1 hour and 72 hour
intervals.
• Display of histograms showing credit unavailability of PFC pause (TxWait and RxWait) for the last
60 seconds, 60 minutes, and 72 hours—You can display this information using the show process
creditmon txwait-history (Fibre Channel) and show system internal {txwait-history |
rxwait-history} (FCoE) commands.
TxWait (or credit unavailability) is caused because of lack of transmit BB_credits (Fibre Channel)
or because of receiving PFC pause frames (FCoE).
There are three graphs for each command and each graph has the most recent second, minute, or
hour unit on the X axis:
1. Seconds scale—Indicates the past 60 seconds, where each column represents a second of time.
Above the histogram are the amounts of time, in milliseconds, that the ports were unable to
transmit and is represented in a vertical format. In the first graph, 8 seconds before the command
being run, there were 857 ms of TxWait (credit unavailability) in the 1-second interval.
2. Minutes scale—Indicates the past 60 minutes, where each column represents a minute of time.
Above the histogram are the amounts of time, in seconds, that the ports were unable to transmit
and is represented in a vertical format. In the second graph, a minute before the command being
run, there was a 22.7 second of TxWait (credit unavailability) in the 1-minute interval.
3. Hours scale—Indicates the past 72 hours, where each column represents an hour of time. Above
the histogram are the amounts of time, in seconds, that the ports were unable to transmit and is
represented in a vertical format. In the third graph, 24 hours before the command being run,
there was a 342 second of TxWait (credit unavailability) in the 1-minute interval. And, 52 hours
prior, there was a 220 second of TxWait.
switch# show process creditmon txwait-history module 1 port 1 | no-more
TxWait history for port fc1/1:
==============================
8999994
5888883
000000076362570000000000000066468354635464357888708700000000
1000 #####
900 ######
800 ######
700 ######
600 ######
500 ######
400 #######
300 #######
200 #######
100 #######
299999999999999999999997
188879888888888889999998
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Cisco MDS 9000 Series Interfaces Configuration Guide, Release 8.x
Information About Congestion Detection
145