Key differences between obj-open and obj-open-by-handled in Pega:
Obj-Open : In Obj-Open, you will get multiple records from a table according to the criteria from the specified class. It also opens an instance of a given class.
OBJ-open-handle : In OBJ-open-handle, you have had to pass the pzInskey as an instance handle. This method opens only one record at a time, and it also opens the object by the handle to the pzInsKey value.
