See $SYSTEM.SQL.SetServerInitCode() (there are differences for IRIS)

Simple example:

Class dc.test
{

ClassMethod Test()
{
  
  s programname=$zcvt(##class(%SYS.ProcessQuery).%OpenId($j).ClientExecutableName,"L")

  i programname="blablabla.exe" {

    ;useful work

    s $EC="ERROR"
    ;or
    s $ROLES="r1"
  }
}

}

USER>d $SYSTEM.SQL.SetServerInitCode("d ##class(dc.test).Test()")

Now, when connecting from a specific program via ODBC/JDBC to namespace "USER", an error will occur. You can configure something another.

See Parent-Child Relationships and Storage

Demonstration:

1. Class dc.child Extends %Persistent
   {
   Property name;
   Property parent As dc.parent;
   // Relationship parent As dc.parent [ Cardinality = parent, Inverse = child ];
   }
   
   Class dc.parent Extends %Persistent
   {
   Property name;
   // Relationship child As dc.child [ Cardinality = children, Inverse = parent ];
   ClassMethod Test()
   {
     d ..%KillExtent()
     d ##class(child).%KillExtent()
     
     &sql(insert into dc.parent(name) values('parent1'))
     &sql(insert into dc.parent(name) values('parent2'))
   
     &sql(insert into dc.child(name,parent) values('child11',1))
     &sql(insert into dc.child(name,parent) values('child12',1))
     &sql(insert into dc.child(name,parent) values('child21',2))
     &sql(insert into dc.child(name,parent) values('child22',2))
     
     zw ^dc.parentD,^dc.childD
   }
   }

   USER>d ##class(dc.parent).Test()
   ^dc.parentD=2
   ^dc.parentD(1)=$lb("","parent1")
   ^dc.parentD(2)=$lb("","parent2")
   ^dc.childD=4
   ^dc.childD(1)=$lb("","child11",1)
   ^dc.childD(2)=$lb("","child12",1)
   ^dc.childD(3)=$lb("","child21",2)
   ^dc.childD(4)=$lb("","child22",2)

2. Important: do not touch the existing Storages in both classes!!!
   

   Class dc.child Extends %Persistent
   {
   Property name;
   //Property parent As dc.parent;
   Relationship parent As dc.parent [ Cardinality = parent, Inverse = child ];
   Storage Default
   {
   ...
   }
   }
   
   Class dc.parent Extends %Persistent
   {
   Property name;
   Relationship child As dc.child [ Cardinality = children, Inverse = parent ];
   ClassMethod Test()
   {
    ...
   }
   Storage Default
   {
   ...
   }
   }

   USER>d ##class(dc.parent).Test()
   ^dc.parentD=2
   ^dc.parentD(1)=$lb("","parent1")
   ^dc.parentD(2)=$lb("","parent2")
   ^dc.childD=4
   ^dc.childD(1,1)=$lb("","child11",1)
   ^dc.childD(1,2)=$lb("","child12",1)
   ^dc.childD(2,3)=$lb("","child21",2)
   ^dc.childD(2,4)=$lb("","child22",2)

3. Important: now remove Storage from dc.child class and recompile both classes. Note that now the Storage of the dc.child class has changed.
   

   USER>d ##class(dc.parent).Test()
   ^dc.parentD=2
   ^dc.parentD(1)=$lb("","parent1")
   ^dc.parentD(1,"child",1)=$lb("","child11")
   ^dc.parentD(1,"child",2)=$lb("","child12")
   ^dc.parentD(2)=$lb("","parent2")
   ^dc.parentD(2,"child",3)=$lb("","child21")
   ^dc.parentD(2,"child",4)=$lb("","child22")
   ^dc.childD=4
   ^dc.childD(1,1)=$lb("","child11",1)
   ^dc.childD(1,2)=$lb("","child12",1)
   ^dc.childD(2,3)=$lb("","child21",2)
   ^dc.childD(2,4)=$lb("","child22",2)

   Now the data in ^dc.childD from the previous test/step is hanging in the air and cannot be accessed via SQL

Based on the above, the answer to your question will depend on what and how exactly you changed in your classes.

PS: for simplicity, I would advise you to create a clone of your dc.child class (without Relationship) and already take the "disappeared" data from it. After linking the tables (possibly with subsequent copying of data from the old Storage to the new one), the clone with the data can be deleted.

See MultiValue Basic | Caché Alternative Exists for SOUNDEX()

Workaround:

Class dc.test [ Abstract ]
{

ClassMethod Test()
{
  
  w ..SOUNDEX("M"),!

  ;or

  &sql(select SOUNDEX('McD') into :r)
  w r,!
}

ClassMethod SOUNDEX(s) As %String [ Language = mvbasic, SqlName = SOUNDEX, SqlProc ]
{
 RETURN SOUNDEX(s)
}

}

Result:

USER>d ##class(dc.test).Test()
M000
M230