I'd strongly recommend to use %Stream since 3.6 MB is huge for a String but not for a PDF.
Besides the absolute maximum of 3.6 MB for %String you may have additional limits of %String.
Dating from ancient ODBC the default max. for Strings is 50 !!!! If you don't set (MAXLEN="") explicitely

I assume you have a PatientID so you might be able to select your records using an INNER JOIN in this way:

SELECT <.......your columns....,contacttype,....> 
FROM my.patient as pat
INNER JOIN 
(select PatientID, MAX(DateFrom) as MaxDate FROM my.patient Group by PatientID) as max
ON  
pat.PatientID=max.PatientID AND pat.DateFrom=max.MaxDate
WHERE  <...whatever... >

so you get the records with the highest DateFrom by Patient
 

if you use Relationship many As obj [ Cardinality = many, Inverse = one ];
you create a managed pointer from many->one  with no sequence of insert.
Though it may be kept if new "many" elements are inserted in sequence with ascending IDs.
Later (manual?) add to the relationship of already exisiting "many" may break this.

To bypass this limitation I see 2 possible solutions:
- you add a property (auto-incremented, insert sequencer) to "many" to keep the insert sequence 
e.g.  Property InsertSequence As %Integer [ InitialExpression = {$increment(^InSeq)} ];
which is rather brute force, but available to manual adjustment for existing data

- you add to "one" side: Property ManyList As %ListOfObjects;
and add your many with Insert() function at and the end of the individual list.
The advantage of this approach is to have the freedom to change the sequence at your needs
And it also allows a kind of m:n relation as you are not limited to add your many to a unique one.
This is not my preferred solution and requires some coding erfort.

in order to provide efficient updates for DeepSee there is a feature named DSTIME.
It writes kind of a log about inserts, deletes, updates. This may suit your requirements.
About 2 years ago I have written an article about the subject. Take a look if this is what you need.
https://community.intersystems.com/post/synchronize-data-dstime


 

Did you ever try this?
  https://learning.intersystems.com/course/view.php?id=28

¡Hola @Kurro Lopez !
It's a really interresting issue.
#2) your second example can't work by principal as you don't pass a call parameter.
#1) It is not foreseen to use object properties as host-variables in SQL
The code fails in the generated Execute method.

set tResult = tStatement.%Execute($g(pObject.KeyProcess),$g(pObject.CodeSpecialist),$g(pObject.CodeProvider),$g(pObject.CodeCenter),$g(pObject.Date))

$GET for oblect-properties is just not ​implemented. It is definded by the class and always there,
But it is required and makes sense for multidimensional properties !

This is valid for ObjectScript as such and not related to SQL.​​​​​​
But in handwritten code you can use $g(NOTHING,pObject.KeyProcess) 
The generator just doesn't do it. 
 

Workaround #1: directly fiddle in the generated code .  Not recommended
Workaround #2:  move your properties with a helper function into local variables
and adjust your query to those variables 

example helper (with obj or id):
ClassMethod FillProp(pObject As Kurro.MyClass) As %Boolean [ SqlName = FILLP, SqlProc ]
{
if '$isObject(pObject) set obj=##class(Kurro.MyClass).%OpenId(pObject)
else  set obj=pObject
set %Kurro("kp")=obj.KeyProcess
     ,%Kurro("sp")= obj.CodeSpecialist
     ,%Kurro("pr")= obj.CodeProvider
     ,%Kurro("cs")= obj.CodeCenter
    ,%Kurro("dt")= obj.Date
quit 1
}
example query;
Query GetInfoRcc(objid As %Integer) As %SQLQuery(CONTAINID = 0, ROWSPEC = "IdList:%String,IdProcess:%String,Duration:%String")
{
    SELECT IdList, IdProcess, Duration
    FROM Kurro.MyClass
    WHERE KeyProcess = :%Kurro("kp")
    AND CodeSpecialist = :%Kurro("sp")
    AND CodeProvider = :%Kurro("pr")
    AND CodeCenter = :%Kurro("cs")
    AND "Date" = :%Kurro("dt")
   AND FILLP(:objid) = 1
}

works as expected.

Sorry for being late. I was interrupted by ....  15 times at least with nonsense

 

There is an example of the WebSocket Server in namespace SAMPLES on Caché only:
in addition there are 4 examples for Caché  on Open Exchange

https://openexchange.intersystems.com/package/WebSocketsSample

https://openexchange.intersystems.com/package/WebSocketsSample

https://openexchange.intersystems.com/package/WebSockets-Tutorial

https://openexchange.intersystems.com/package/WebSocketClient-js

try:

;
set file=$system.Util.ManagerDirectory()_"messages.log"
open file:("RS"):1 w $T  open 2:99
try { for n=1:1 use file read lin use 2 write lin,! } catch { close 2,file  write n_" lines",! }
;

then use ^SPOOL mapping (OEX) to work on it with SQL

Mirroring is also available in Caché