Re: list of open descriptors

[CRPence <CRPbottle@xxxxxxxxx>]

On 06 Jun 2013 13:17, Vernon Hamberg wrote:
> I saw that - it says to use 0 to get the current maximum for the job
> - 32K by default.

  Actually I believe the documented number is 200 by default; i.e. the 
API would need to have been called to increase the count by 31800 to 
establish a maximum of 32K:
http://pic.dhe.ibm.com/infocenter/iseries/v7r1m0/topic/rzamp/rzamp.pdf
"...
Default maximum number of socket and file descriptors per job: 200
Maximum number of socket and file descriptors per job: 2 500 000
 ..."

> I didn't see that the function returns what anything like what is in
> USE - that is, how many open files there are.

  Reread carefully, both of the "A request to decrease the maximum", 
plus my implementation suggestion [following the i.e. in my earlier 
quoted message].  That starts with the known maximum, tries to decrease 
the maximum to 20, then resets the maximum.  It should become obvious 
when rereading the docs, paying *close attention* to the references to 
the word "open".?  Or perhaps I misread the documentation.?  Or perhaps 
the following pseudo-code [thus obviously untested] helps; and someone 
could test by converting to actual code, to verify the effects in a job 
with more than 20 open files [or active descriptors] and a job with 
fewer than 20 open files [or active descriptors]:

    // the "@" implies a pointer; the implementation may be different
    // according to the prototype.  The variable name without the "@"
    // represents the integer value at that location
    fDescErr = DosSetRelMaxFH( 0 : fDsecMax@ ) ; // set fDescMax
    if fDescErr < 0 ; // all bad; bail!
    endif ;
    fDescAdd = 20 - fDescMax ; // "decrease by" this value
    fDescErr = DosSetRelMaxFH( fDescAdd@ : fDescNbr@ ) ;
    if fDescErr < 0 ; // all bad; bail!
    endif ;
    // at this point fDescNbr has the number of in-use descriptors,
    // *or* the value of 20
    fDescAdd = fDescMax - fDescNbr ; // "increase by" this value
    fDescErr = DosSetRelMaxFH( fDescAdd@ : fDescOrg@ ) ; // Reset to 
Original
    if fDescErr < 0 ; // all bad; bail!
    endif ;
    if fDescMax <> fDescOrg ; // assert; if true, then logic error
    endif ;

> This is still an interesting function!

  And per the reference in another message to the Software Technical 
Document 631474304 with Document Title: File Descriptor Limits In the 
Qshell and PASE Environments, that may be _the_ way to get the count if 
the count is greater than 20.  My interpretation of the final line about 
opening "a service request with IBM Software Support" is that the 
inquiry will result not in access to some undocumented API, but a means 
to find the information via some kind of dump, possibly only within SST:
http://www-912.ibm.com/s_dir/SLKBase.nsf/1ac66549a21402188625680b0002037e/4d634afb140069dc862579e60055f256?OpenDocument

Regards, Chuck

> On 6/6/2013 11:08 AM, CRPence wrote:
> > On 05 Jun 2013 19:59, Mike Krebs wrote:
> > > <<SNIP>>
> > >
> > > What is the command or API that will show the list of open
> > > descriptors or the number of open descriptors in a job?
> > For the latter question, "the number of open descriptors in a
> > job", the DosSetRelMaxFH() (Change Maximum Number of File
> > Descriptors) API *apparently could be used* [probably not a
> > desirable means] to determine that information for any value over
> > twenty; i.e. by requesting to decrease the maximum number of file
> > descriptors to twenty... and then presumably, to reset the maximum
> > to its original value that was saved on a prior invocation to
> > retrieve that maximum.
> >
> > http://pic.dhe.ibm.com/infocenter/iseries/v7r1m0/topic/apis/dossrmfh.htm
> > _i DosSetRelMaxFH()--Change Maximum Number of File Descriptors i_
> > "...
> > The DosSetRelMaxFH() function requests that the system change the
> > maximum number of file descriptors for the calling process (job).
> > The system preserves all file descriptors that are currently open.
> >
> > ...
> >
> > A request to decrease the maximum number of file descriptors will
> > succeed. The resulting maximum will be the smallest number
> > possible, but may be more than what you expected. For example,
> > assume that the current maximum is 200 and there are 150 open
> > files. A request to decrease the maximum by 75 results in the
> > maximum being decreased by only 50, to 150, to preserve the open
> > file descriptors.
> >
> > A request to decrease the maximum number of file descriptors to
> > below 20 will succeed, but the maximum will never be decreased
> > below 20.
> >
> > To retrieve the current maximum number of file descriptors,
> > without any side effects, the value pointed to by pcbReqCount
> > should be set to zero.
> > ..."