Re: OpenVMS locking out connection requests (490 Views)
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Occasional Advisor
Max_Jarvis
Posts: 9
Registered: ‎10-14-2011
Message 1 of 10 (649 Views)

OpenVMS locking out connection requests

Hi,

 

I am having a problem with an FTP client application, working with an OpenVMS server.

 

This is a Windows PC application, using FTP client support provided in Windows. It retrieves files from an OpenVMS server (v8.3 1H1). It has been working fine for a long time, but I have recently moved it to a new and slightly faster PC and now it doesn't work properly.

 

What happens is this: it starts off fine, retrieves maybe two or three hundred files (the number varies), then an FTP transaction fails. Windows reports error code 12031, which apparently means 'connection with server was reset'. Once this has happened, the OpenVMS server completely refuses to have anything to do with the PC. Unrelated TELNET connections are closed down and won't re-open, in fact the PC can't even ping the server. This impasse does eventually clear. I haven't yet got to the bottom of when or why it clears, but it looks as if you have to leave the server alone for a few minutes and then it relents. For example, if you try to ping it once a minute you never seems to get through, but if you leave it alone for five minutes then try, it works.

 

As an experiment I have modified the FTP application to delay for 150 milliseconds between fetching each file and the next. This makes the problem go away (but it makes the job take much longer).

 

It looks as if there's something in OpenVMS which says "STOP, you're working me too hard, I refuse to go on at this rate", i.e. some sort of overload protection?

 

Does anybody know anything about this? All suggestions gratefully received.

 

 By the way, both PCs run the same version of Windows (XP SP3).

 

Thanks in advance,

Max.

 

 

Respected Contributor
Bob Blunt
Posts: 314
Registered: ‎05-01-2003
Message 2 of 10 (642 Views)

Re: OpenVMS locking out connection requests

I think I'd start by looking at the logfiles on the OpenVMS system(s) in question.  It sounds like you're either exceeding a limit set in IP Services setup or, possibly, some UAF parameter for one of the servers.  Frankly your move to the "faster and newer" PC has probably exposed this limitation because the older, slower one never quite got to that threshold.  It does sound "fixable" on the VMS side but, again, you'll probably have to check the logs, OPCOM output or watch the consumed values for the various services that IP Services provides.  It might also be advantageous to locate one of the many process quota monitor DCL programs and watch the individual IP Services server and/or daemon processes to see if some resource is being exhausted.

 

bob

Honored Contributor
Steven Schweda
Posts: 9,096
Registered: ‎02-23-2005
Message 3 of 10 (641 Views)

Re: OpenVMS locking out connection requests

Occasional Advisor
Max_Jarvis
Posts: 9
Registered: ‎10-14-2011
Message 4 of 10 (635 Views)

Re: OpenVMS locking out connection requests

Many thanks for prompt replies....

 

I am no expert on OpenVMS and don't know where to look for 'log files', can anyone help? I've looked in sys$manager:operator.log, nothing of interest there. I thought I was on to something when I saw that there are a couple of sys$manager:tcpip$ftp_server.log files, but they are dated March 2011. Ho hum.

 

I have looked at the OpenVMS server during the period after the failure when it won't respond to the FTP client PC , and it does not crash. It continues to perform all its other functions properly, including some which do a lot of TCP/IP comms all the time. I don't see any OPCOM output either.

 

During the period when the failing FTP client PC can't ping the server, other PCs can ping it without trouble. But no connection from the FTP client PC can get through, I've tried ping and I've tried starting a new Telnet connection, and existing Telnet connections get disconnected.

 

I'm being vague about the length of the period when the OpenVMS server won't talk to the PC not because I forgot to mention it, but because I don't know how long it is, or even if it's always the same length. Experiments continue.

 

TCPIP version is v5.6 ECO 2. Machine is an rx2660.

 

Honored Contributor
Steven Schweda
Posts: 9,096
Registered: ‎02-23-2005
Message 5 of 10 (630 Views)

Re: OpenVMS locking out connection requests

Occasional Advisor
Max_Jarvis
Posts: 9
Registered: ‎10-14-2011
Message 6 of 10 (609 Views)

Re: OpenVMS locking out connection requests

The other PC (the one that can ping the OpenVMS server when the failing FTP client PC can't) is on the same network segment, in fact it's plugged into the same switch.

 

The FTP_RUN log file is a useful discovery, thanks for that.

 

Here is a successful run using the FTP client on the older PC, on 10.66.21.254:

 

%TCPIP-I-FTP_SESCON, FTP SERVER: session connection from 10.141.66.254 at 30-NOV-2012 16:49:51.77

%TCPIP-I-FTP_NODE, client host name: 10.141.66.254

%TCPIP-I-FTP_USER, user name: export

%TCPIP-I-FTP_OBJ, object: SYS$SYSDEVICE^:^[EXPORT^]

%TCPIP-I-FTP_CHINFO, TCPIP$FTPC0002D: Failed to set default directory

%TCPIP-E-FTP_BADDIR, invalid directory

%TCPIP-I-FTP_USER, user name: export

%TCPIP-I-FTP_SESDCN, FTP SERVER: session disconnection from 10.141.66.254 at 30-NOV-2012 16:50:10.53

 

The FTP client logs in as user EXPORT. There are messages about ‘Failed to set default directory’, which don’t matter, they are there because there is no directory on the server named [EXPORT], since it isn’t necessary.

 

Here is a failed attempt with the same FTP client on the newer PC. The PC is on 10.141.66.21.

 

%TCPIP-I-FTP_SESCON, FTP SERVER: session connection from 10.141.66.21 at 30-NOV-2012 15:32:34.18
%TCPIP-I-FTP_NODE, client host name: 10.141.66.21
%TCPIP-I-FTP_USER, user name: export
%TCPIP-I-FTP_OBJ, object: SYS$SYSDEVICE^:^[EXPORT^]
%TCPIP-I-FTP_CHINFO, TCPIP$FTPC0002C: Failed to set default directory
%TCPIP-E-FTP_BADDIR, invalid directory
%TCPIP-I-FTP_NODE, client host name: 10.141.66.21
%TCPIP-I-FTP_USER, user name: export
%TCPIP-I-FTP_OBJ, object: 10.141.66.21
%TCPIP-I-FTP_CHINFO, TCPIP$FTPC0002C: Error building data connection
%SYSTEM-F-TIMEOUT, device timeout
%TCPIP-I-FTP_USER, user name: export
%TCPIP-I-FTP_SESDCN, FTP SERVER: session disconnection from 10.141.66.21 at 30-NOV-2012 15:42:54.31

 

The difference is these two messages:

 

%TCPIP-I-FTP_CHINFO, TCPIP$FTPC0002C: Error building data connection
%SYSTEM-F-TIMEOUT, device timeout

 

So it looks like some sort of timeout issue. Any idea which timeout this might be, or what ‘device’ refers to? I'm wondering whether it might actually be a timeout in the PC - maybe TCP/IP in the newer PC is configured differently from the old PC? I'll look into that....

 

By the way, the client transfers lots of files. On this failed attempt it had successfully transferred 1084 files, taking about 10 seconds, before the problem occurred and the client exited. The time at the top (15:32:34.18) is the time when the FTP client started transferring files, and I’m fairly certain the time at the bottom (15:42:54.31) is the time when the server re-allowed connections from the PC, e.g. pings.

Honored Contributor
Steven Schweda
Posts: 9,096
Registered: ‎02-23-2005
Message 7 of 10 (605 Views)

Re: OpenVMS locking out connection requests

Honored Contributor
John Gillings
Posts: 2,995
Registered: ‎07-31-2003
Message 8 of 10 (551 Views)

Re: OpenVMS locking out connection requests

Could be a duplex mismatch.

 

Check that the speed and duplex settings on ports on each end of all cables involved are set the same. I recommend "autoconfigure".

 

Unfortunately, mismatched settings result in a configuration which "works" until you give it load.

 

Don't assume the settings are correct. In the face of this type of symptom, they need to be confirmed.

A crucible of informative mistakes
Occasional Advisor
Max_Jarvis
Posts: 9
Registered: ‎10-14-2011
Message 9 of 10 (499 Views)

Re: OpenVMS locking out connection requests

Progress report: the failing PC can do other network stuff at the time when it can't connect to the OpenVMS server, so I still don't know which end is at fault. By the way, I don't know about speed and duplex settings on the cables involved: they are all Ethernet cables between switches, ordinary CAT5 cables, all in the same building. The two PCs (the one that works and the one that fails)  seem to be set up identically as regards TCP/IP; in fact under Windows XP, TCP/IP seems to be largely self-configuring. In any case, I'm a bit reluctant to adjust standard settings on either the OpenVMS server or the PC client, so I decided to experiment with a pair of home-made applications to  send large amounts of data back and forth between PC client and OpenVMS server, just using simple network sockets, no FTP. That seems to work fine, so the problem may be in the FTP implementation in Windows, at least some of which comes from the out-of-date compiler and libraries I have to use. So my solution will  probably be to write a pair of custom-built file transfer programs for this specialised application, and forget about FTP. Many thanks to those who posted replies.... Max.

Respected Contributor
Bob Blunt
Posts: 314
Registered: ‎05-01-2003
Message 10 of 10 (490 Views)

Re: OpenVMS locking out connection requests

Max, you might look at this information and engage someone who has more OpenVMS savvy (there are several OpenVMS consultants available if needed) if necessary:

 

http://h71000.www7.hp.com/doc/83final/6526/6526pro_041.html#ftp_logicals_sec

 

In particular you might, for a BRIEF time, setup the TCPIP$FTPD_LOG_CLIENT_ACTIVITY to try and pinpoint what each session is experiencing.  Depending on the load involved it might not be too bad to leave it "on" for longer but I'd suggest keeping an eye on the volume of information to make sure that the system disk doesn't fill up.

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