Re: Check existence of data area in ILE C

On 10-Mar-2015 03:27 -0500, Zvi Kave wrote:

On 16/12/2014 11:18, Zvi Kave wrote:

On 15/12/2014 20:14, Jevgeni Astanovski wrote:

On Mon, Dec 15, 2014 at 6:52 PM, Zvi Kave wrote:

My ILE C program crashes in the line of QXXRTVDA if data does not
exist.
Is there a way to avoid this crash ?
Someone has an example code for this?

The line is like this:
QXXRTVDA(dta, 41, 5, user_dta);

and I got program crash with the message:
"Data area DTA in QGPL not found."

If data area dta exists, it works fine.

I use a function Check_DAARA before calling RTVDTAARA:

int Check_DTAARA(char *dtaname, char *dtalib)
{
_SYSPTR p;
volatile _INTRPT_Hndlr_Parms_T ca; /* communications area */

#pragma exception_handler(ERROR_OCCURED, ca, 0, _C2_MH_ESCAPE, \
_CTLA_HANDLE, "MCH3401")

p = rslvsp(WLI_DTAARA, dtaname, dtalib, 0x0190);
return 0;

ERROR_OCCURED:
return -1;
}

Returns 0 if data area exists, otherwise -1.
Requires some includes.
Can be used as a generic exception handler.
It is actually made of an example in one of the manuals (ILE/C
programmers's guide or alike).

I tried this function and it works fine!
I only added these 2 includes:
#include<except.h>
#include<mih/rslvsp.h>

I realized that every call to Check_DTAARA when data area not
exists, creates error lines in job log like this (which almost fired
me out):
msg MCH3401: "Cannot resolve to object DTANAME. Type and Subtype X'190A' Authority X'0000'.

Do you have quick solution to avoid of message in job log ?

The exception causes a message, and that message can optionally be removed. For example, the "Message Action" argument of the Receive Program Message (QMHRCVPM) API can be set to '*REMOVE' to request that the API remove the Escape message that was just handled.

However if that is done, then using a /check existence of data area/ preceding the request to retrieve the data seems folly; likely both coding the exception_handler for the effectively identical condition and dealing with the messaging from the code in the OP is sufficient. Inserting the Rslvsp before the QXXRTVDA allows a window of opportunity for concurrent operations [e.g. Delete Data Area (DLTDTAARA)] to occur that would give rise to effectively the same error seen originally; i.e. a check for existence in one instant is not preventive to a lack of existence an instant [or anytime] later. Probably just best to code the call to the /Retrieve Data Area/ [e.g. QXXRTVDA or QWCRDTAA] in a presumed-success manner, asking to access the data area or perhaps to inform of the condition of the absence, thus eliminating the window of opportunity for the identical problem that was described in the OP.

The following link has an example of QMHRCVPM API being invoked, but with the Message Action defined _to mark the message_ as /old/ instead of _removing_ the message; the next link is to that API for which the #include <qmhrcvpm.h> would be coded to access the definition from QSYSINC/H:
<http://www.ibm.com/support/knowledgecenter/api/content/ssw_ibm_i_71/apiref/apiexdirep.htm>
<http://www.ibm.com/support/knowledgecenter/ssw_ibm_i_71/apis/QMHRCVPM.htm>