TS/MP Pathsend and Server Programming Manual (G06.24+, H06.03+)

Writing Pathway Servers

NonStop TS/MP Pathsend and Server Programming Manual–132500

4-11

Considerations for Debugging Pathway Servers

When you are running a Pathway server in debug mode (that is, with the server class

configured with DEBUG ON) or when the server falls into debug mode because of an

error, some situations might cause errors to be returned to the requester communicating

with that server, and in some cases also might cause errors to be returned to other

requesters. Those situations are described in the following subsections.

LINKMON Process and TCP Timeouts

The LINKMON process and the TCP have a built-in five-minute timeout for process

opens and I/O operations such as get-link requests. During normal operation, such

operations are generally completed in less than five minutes unless there is a problem.

However, if the server process is in debug mode, the server can be stopped (for example,

at a breakpoint) for longer than five minutes. In certain cases, this can cause a process

open or I/O operation from a LINKMON process or TCP to time out. The effects of the

timeout depend on what type of operation timed out.

If an I/O operation to the PATHMON process times out, the LINKMON process or the

TCP behaves as if there were a problem with the PATHMON process: that is, it shuts

down communication with the PATHMON process, relinquishing all links granted by

that PATHMON process.

In this situation, if the requester that sent the request that timed out was a Pathsend

requester, this request (as well as all other server-class send requests queued under that

PATHMON process) fails with Pathsend error 902, FEScPathmonConnect, with

file-system error 40 (timeout error). Subsequent send requests to server classes under

that PATHMON process fail with Pathsend error 915, FEScPathmonShutDown.

If the timed-out request came from a SCREEN COBOL requester, this request (as well

as all other server-class send requests queued under that PATHMON process) fails with

a SEND error with a TERMINATION-STATUS value of 18 (PATHMON I/O error) and

a TERMINATION-SUBSTATUS value of 40. Subsequent send requests to server classes

under that PATHMON process fail with a SEND error with a TERMINATION-STATUS

value of 18 (PATHMON I/O error) and a TERMINATION-SUBSTATUS value of 40.

If a timeout occurs on the server process open, the LINKMON process or the TCP

returns the link to the PATHMON process. If other links to the server class exist, no send

requests fail as a result of the open failure. If no other links exist, the send request (as

well as all other server-class send requests queued for that LINKMON process or TCP)

fails. A Pathsend requester receives Pathsend error 904, FEScServerLinkConnect, with

file-system error 40 (timeout error). A SCREEN COBOL requester receives a SEND

error with a TERMINATION-STATUS value of 12 (I/O error) and a TERMINATION-

SUBSTATUS value of 40 (timeout error).

Note also that if the server class is configured so that it can be opened more than once

(that is, with MAXLINKS greater than 1), a LINKMON process or TCP can attempt to

open a server process in that server class at any time. This open attempt can time out if

the server process is being debugged.