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Question Adrian Bourner · Feb 14, 2019

Accessing the lock table and another process's variables, potentially on a different server

#Caché

Hi Community,

I have a need to access the Lock Table to find the Process ID of the process that has a particular global node Locked. The process holding the lock could be on any one of four application servers.

Having identified the Process ID, I then need to interrogate the local variables for that process, to find an application User ID.

I can then inform the current user which of their colleagues has a particular record locked, preventing them from continuing with their work...

Are these things I can do under Caché? If so, how would I do so?

In any answers, please bear in mind that I am mostly just a fusty old MUMPS programmer, from what increasingly seems like the dark ages, who did most of his coding in DSM for Open VMS!

Thanks,

Adrian

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Vitaliy Serdtsev · Feb 15, 2019

See:

%SYS.LockQuery

PS: $SYSTEM.Util.CleanDeadJobs().

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Adrian Bourner Feb 15, 2019 to Vitaliy Serdtsev

Thanks for the pointers, and I have located those in the documentation.

However, if I follow that, I get:

HCSLIVE>S Rset=##class(%ResultSet).%New("%SYS.LockQuery:List")

IHCSLIVE>zw

Rset=<OBJECT REFERENCE>[1@%Library.ResultSet]

IHCSLIVE>zw Rset

Rset=<OBJECT REFERENCE>[1@%Library.ResultSet]

IHCSLIVE>D Rset.Execute("")

IHCSLIVE>zw

Rset=<OBJECT REFERENCE>[1@%Library.ResultSet]

IHCSLIVE>zw Rset

Rset=<OBJECT REFERENCE>[1@%Library.ResultSet]

IHCSLIVE>W $O(Rset(""))

IHCSLIVE>

i.e. there doesn't seem to be anything there I can work with.

I suspect that I lack some basic understanding of working with classes...

Thanks,

Adrian

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Vitaliy Serdtsev Feb 15, 2019 to Adrian Bourner

Using Dynamic SQL Dynamic SQL Using Older Result Set Classes

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Adrian Bourner Feb 15, 2019 to Vitaliy Serdtsev

Hi Vitaliy,

Thanks again for your ongoing help with this.

I have now accessed the Lock Table (on the current node, anyway), and identified the PID of the process that has the Lock that I am interested in.

I can see from the help how to use %SYS.ProcessQuery:VariableByPid

However, if I try -

S Vars=##class(%ResultSet).%New("%SYS.ProcessQuery:VariableByPid(6460,zPRS)")

which I know from the System Management Portal exists for that PID, and therefore would have expected to return the value of zPRS from PID 6460, I don't get what the help seems to indicate -

IHCSLIVE>W Vars.zPRS
^
<INVALID OREF>

I guess I'm still missing something fundamental?

Thanks,
Adrian
(btw, this is my first-ever foray into Caché's world of classes and objects - essentially, I am "just" an old MUMPSter)

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Vitaliy Serdtsev Feb 18, 2019 to Adrian Bourner

Hi Adrian.

Made a small example:

<FONT COLOR="#0000ff">#dim </FONT><FONT COLOR="#800000">rs </FONT><FONT COLOR="#0000ff">As </FONT><FONT COLOR="#008080">%ResultSet
   
</FONT><FONT COLOR="#0000ff">s </FONT><FONT COLOR="#800000">pid</FONT><FONT COLOR="#000000">=4652
   
</FONT><FONT COLOR="#0000ff">s </FONT><FONT COLOR="#800000">rs</FONT><FONT COLOR="#000000">=</FONT><FONT COLOR="#000080">##class</FONT><FONT COLOR="#000000">(</FONT><FONT COLOR="#008080">%ResultSet</FONT><FONT COLOR="#000000">).</FONT><FONT COLOR="#0000ff">%New</FONT><FONT COLOR="#000000">(</FONT><FONT COLOR="#008000">"%SYS.ProcessQuery:VariableByPid"</FONT><FONT COLOR="#000000">)
   
</FONT><FONT COLOR="#0000ff">f </FONT><FONT COLOR="#800000">filter</FONT><FONT COLOR="#000000">=</FONT><FONT COLOR="#008000">""</FONT><FONT COLOR="#000000">,</FONT><FONT COLOR="#008000">"a*" </FONT><FONT COLOR="#800080">{
 </FONT><FONT COLOR="#0000ff">w </FONT><FONT COLOR="#000000">!,</FONT><FONT COLOR="#008000">"Filter = "</FONT><FONT COLOR="#000000">,</FONT><FONT COLOR="#0000ff">$$$quote</FONT><FONT COLOR="#000000">(</FONT><FONT COLOR="#800000">filter</FONT><FONT COLOR="#000000">),!
 </FONT><FONT COLOR="#0000ff">d </FONT><FONT COLOR="#800000">rs</FONT><FONT COLOR="#000000">.</FONT><FONT COLOR="#0000ff">Execute</FONT><FONT COLOR="#000000">(</FONT><FONT COLOR="#800000">pid</FONT><FONT COLOR="#000000">,,,,</FONT><FONT COLOR="#800000">filter</FONT><FONT COLOR="#000000">)
 </FONT><FONT COLOR="#0000ff">while </FONT><FONT COLOR="#800000">rs</FONT><FONT COLOR="#000000">.</FONT><FONT COLOR="#0000ff">Next</FONT><FONT COLOR="#000000">() </FONT><FONT COLOR="#800080">{
   </FONT><FONT COLOR="#0000ff">w </FONT><FONT COLOR="#008000">"Name = "</FONT><FONT COLOR="#000000">,</FONT><FONT COLOR="#800000">rs</FONT><FONT COLOR="#000000">.</FONT><FONT COLOR="#0000ff">Get</FONT><FONT COLOR="#000000">(</FONT><FONT COLOR="#008000">"Name"</FONT><FONT COLOR="#000000">),</FONT><FONT COLOR="#008000">", Value = "</FONT><FONT COLOR="#000000">,</FONT><FONT COLOR="#800000">rs</FONT><FONT COLOR="#000000">.</FONT><FONT COLOR="#0000ff">Get</FONT><FONT COLOR="#000000">(</FONT><FONT COLOR="#008000">"Value"</FONT><FONT COLOR="#000000">),!
 </FONT><FONT COLOR="#800080">}
}</FONT>

Result:

USER:4652><FONT COLOR="#0000ff">s </FONT><FONT COLOR="#800000">a</FONT><FONT COLOR="#000000">=</FONT><FONT COLOR="#008000">"11"</FONT><FONT COLOR="#000000">,</FONT><FONT COLOR="#800000">b</FONT><FONT COLOR="#000000">=</FONT><FONT COLOR="#008000">"22"</FONT><FONT COLOR="#000000">,</FONT><FONT COLOR="#800000">a1</FONT><FONT COLOR="#000000">=</FONT><FONT COLOR="#008000">"33" </FONT><FONT COLOR="#0000ff">w $job</FONT>
4652
USER:1392><FONT COLOR="#0000ff">w $job</FONT><FONT COLOR="#000000">,! </FONT><FONT COLOR="#0000ff">d </FONT><FONT COLOR="#000000">^dc</FONT>
1392
Filter = ""
Name = a, Value = 11
Name = a1, Value = 33
Name = b, Value = 22
Filter = "a*"
Name = a, Value = 11
Name = a1, Value = 33

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Eduard Lebedyuk · Feb 18, 2019

Would process user not cut it?

You can later convert it into app user if you have 1:1 matching.

It would work faster than getting local variables.

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