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· 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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Adrian Bourner · Feb 15, 2019

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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Adrian Bourner · Feb 15, 2019

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

Hi Adrian.

Made a small example:

#dim rs As %ResultSet
   
s pid=4652
   
s rs=##class(%ResultSet).%New("%SYS.ProcessQuery:VariableByPid")
   
f filter="","a*" {
 w !,"Filter = ",$$$quote(filter),!
 d rs.Execute(pid,,,,filter)
 while rs.Next() {
   w "Name = ",rs.Get("Name"),", Value = ",rs.Get("Value"),!
 }
}

Result:

USER:4652>s a="11",b="22",a1="33" w $job
4652

USER:1392>w $job,! d ^dc
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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