Kbase 1216: TCP and FTP performance issues with record locking
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
10/05/1998 |
|
TCP and FTP performance issues with record locking
911007-sal01Encountering the "Silly Window Avoidance" issue with TCP software. On
a recent test with DOS PC using FTP it was found that running two for
each programs with the customer file gave very different results if
you used the NO-LOCK option. The NO-LOCK would run in 20 seconds where
as the FOR-EACH (with locking) took over 5 minutes. The reason is an
addition to TCP software to prevent a problem with packets being lost.
They added a session level ackknowledgement which became known as the
"Silly window avoidance". The problem we have is that the LOCKREL that
we use to send lock acknowledgement is one directional and will not
send back acknowledgement. Therefore the issue of time is the fact
the lockrel by not sending back an acknwledgement, will have to wait
for the FTP to time out each time before sending another lockrel. The
time outs can take 2-5 seconds each, which will quickly add up.
We have seen this same occurance in Unix with TCP as well. As
workaround we have added SETSCOKOPT(no delay) to prevent the request
for acknowledgement from the lockrel call. However not all TCP
software will will support it as is the case in this version of FTP.
Testing was with version 6.2H. In further testing we discovered that
Lan Workplace for DOS worked fine, so that could be a valid
alternative.
Progress Software Technical Support Note # 1216