topic Re: data over run in decnet task to task communication in Operating System - OpenVMS

data over run in decnet task to task communication

RAVIKANTH_3 — Mon, 11 May 2009 07:03:04 GMT

Hi

I have decnet task to task communication, where say process x communicates with process y. Process x writes into mailbox some data and process y reads that data from mailbox. All this is implemented using sys$qiow system call. I getting error "%SYSTEM-W-DATAOVERUN, data overrun".

I traced the reason for this error, every where they are suggesting to increase the RMS buffer using set rms_default /networkblockcount. I have tried that but no success.

Same code worked for many years and now it is causing the problem. Seems strange, not able to figure out the problem.

Could any one help me in solving this.

Re: data over run in decnet task to task communication

Volker Halle — Mon, 11 May 2009 08:17:22 GMT

If you're using $QIOWs, then you're NOT using RMS. This is why setting an RMS parameter does not help.

Can you identify the failing QIOW in your code ? Run the program with the debugger and check all parameters. Find out, how much data the other side has actually sent.

Volker.

Re: data over run in decnet task to task communication

RAVIKANTH_3 — Mon, 11 May 2009 08:30:49 GMT

hi

process x sends request using sys$qiow.
Process y reads the request as shown below

vf_l_status = SYS$QIOW(,%VAL(vh_t_lnkchn), %VAL(IO$_READVBLK),
vg_t_central_io,,,
%REF(vg_t_oprequest),
%VAL(kh_t_cdmrequestlen),,,,)

vg_t_central_io.vh_iosb_iosts) is giving data over flow error during run time.

If its not RMS what could be the problem for data over run.

Re: data over run in decnet task to task communication

Robert Gezelter — Mon, 11 May 2009 09:40:05 GMT

Ravikanth,

Please review the relevant material in the Guide to Networking.

Unlike TCP, which is stream-based, DECnet task level communictions (using NSP) is message based. The entire message must fit within the buffer.

Check the length of the message sent, and check the size of the receiving buffer. Check the documentation, the IOSB will contain details.

- Bob Gezelter, http://www.rlgsc.com