Hey Ashok.

I think there's a slight correction needed for your code snippet.

Specifically, for the line "do object.Organizations.GetAt(key).%DeleteId(key)" the DeleteId using the value of Key will not be the correct value to delete the intended object.

Should the code block instead be:

ClassMethod %OnDelete(oid As %ObjectIdentity) As %Status [ Private, ServerOnly = 1 ]
{
    Set object = ..%Open(oid,,.status)
    If $$$ISERR(status) Quit status
    If $ISOBJECT(object.Organizations) {
        Set org= object.OrganizationsGetSwizzled()
        While org.GetNext(.key){
            Set tID = object.Organizations.GetAt(key).%Id()
            Do object.Organizations.GetAt(key).%DeleteId(tID)
        }
    }
    Quit $$$OK
}