AllAccepted answers
Robert Cemper · Nov 1, 2018

I discourage since years the use of $ZU(...) functions as they aren't documented since 2010. 
I recently had to dig back to 2009 for just a weak hint what might happen.

It is even worse with all the internal stuff around %occ* and similar.
No docs. No guaranty of the life cycle. No (external) notice of eventual changes. Mostly as a deployed code.

If it is used inside a $system.* or part of a generated code that's OK. The responsibility is not at the user side.

Verifying those "specials" with every release change can be a very heavy exercise. 
(just experiencing this on a system locked down to on an older version unable to migrate)

Robert Cemper · Nov 1, 2018

not being verbose in %occ* world I had this solution also allowing to change quoting
 

parseCSV(string,newsep,sep=",",quote="""",newquote) {    ;adjust for flexible quoting
  set res="",newsep=$g(newsep,$c(9)),newquote=$g(newquote,quote)
  for  { 
     if $g(string)[sep { 
       if $e(string)=quote {
          set part=$P(string,quote,2),string=$p(string,part_quote_sep,2,*)
                ,res=res_newquote_part_newquote_newsep }
     else  { 
         set part=$P(string,sep),string=$p(string,sep,2,*)
               ,res=res_part_newsep } 
    } else  { 
          set res=res_$g(string) quit }
     }
  quit res
}

BTW.
It's an excellent test exercise for new COS programmers
I'll add it to my collection.

Thanks   yes
 

Robert Cemper · Oct 21, 2018

OK.  for some reason the most important part of the link was truncated.

https://docs.intersystems.com/latest/csp/documatic/%25CSP.Documatic.cls?PAGE=CLASS&LIBRARY=%25SYS&CLASSNAME=%25CSP.BinaryStream

I hope it doesn't hide again.

The basic mistake happens here the definition of Request 
https://docs.intersystems.com/latest/csp/documatic/%25CSP.Documatic.cls?PAGE=CLASS&LIBRARY=%25SYS&CLASSNAME=%25CSP.Request

And you are right. %CSP.Stream has no Read method because  ContentType tells you the true object . 
As in the example:

It could have been %CSP.CharacterStream as well.

Both extend over some steps %GlobalStreamAdaptor which have all the READ, WRITE, ....methods

Just reading docs and not checking inherited methods (e.g. in Studio) is mostly misleading.

Robert Cemper · Oct 18, 2018

Just adding CACHESYS to mirror could be a deadly exercise

Who then is primary? Me or my Mirror?

But to achieve your goal you may have an additional DB. Let's name it SYSMIRROR
And now you use global / subscript level mapping to place the common information there.
e.g. ^SYS("Security") or parts of it ("RolesD","UsersD", ..)  whatever you think you need.
I never tried it but it could not see a contradiction.

For better synchronization and uniqueness, I'd personally prefer to have this SYSMIRROR accessed over ECP while holding a local copy of SYSMIRROR for backup /  failover

Robert Cemper · Oct 17, 2018

YES it is possible.

- see your sub_query first working 
- just custom_view seems to miss the typical dot in table and view names 

Views are just a kind of shortcut to a query formula.

 in namespace SAMPLES you could do this

select Home_City, DOB, name,
(select Name from sample.personview sub where sub.DOB=main.DOB ) SubName
 from Sample.Person main

The example doesn't make much sense but it shows that this works

Anyhow, why don't you just use a JOIN  like this?

select Home_City,main.DOB, main.name, sub.name
from Sample.Person main
left outer join sample.personview sub onsub.DOB=main.DOB

or in your case 

select    MsgId,   FileName, ReportName
from main_table LEFT OUTER JOIN   custom_view
ON     MsgId = ReportId

Again: both table name and view name look odd to me

 

Robert Cemper · Oct 10, 2018

for pure object access, you have a getter and a setter method.  no magic

if also want to use it for SQL
- you need SqlComputed code. This will also replace your (object)Getter.

- to set your local variable also by INSERT or UPDATE you need to add  UPDATE and INSERT Trigger code.

example;

Class DC.Setter Extends %Persistent [ Not ProcedureBlock ]
{
Property DUZ As %String [ Calculated, SqlComputed, SqlColumnNumber = 2,
       SqlComputeCode = {set {*} = DUZ(2)}  ];

// for settig object property
Method DUZSet(Arg As %String) As %Status [ ServerOnly = 1 ]
{  set DUZ(2)=Arg  Quit $$$OK   }

Trigger UpdTrigger [ Event = UPDATE ]
{ set DUZ(2)= %d(2) ,%ok=1 }
Trigger InsTrigger [ Event = INSERT ]
{ set DUZ(2)=  %d(2) ,%ok=1 }

--

To anticipate critics:
Some people may say it's dirty coding.  YES !! But it works.