Actual Use Cases for %Stream.DynamicBinary and %Stream.DynamicCharacter

%Stream.DynamicBinary it's a stream that use a different storage, if you need your data in a  %Stream.TmpCharacter just copy the stream using CopyFrom() method.

Both %Stream.DynamicBinary  and %Stream.TmpCharacter are %StreamObject descendant, the use/have the same interface (methods) but a different storage.

%Stream.Dynamic* are read-only pointers to DAO data. %Stream.Tmp* are full-fledged (r/w) in-memory streams.

The %Stream.DynamicCharacter (%SDC) and %Stream.DynamicBinary (%SDB) classes are designed to hold a copy of the string data that is in an element of a %DynamicArray (%DA) or a %DynamicObject (%DO) class.  The %SDC class, and its %SDB subclass, were designed to be small and efficient even when the string in the %DA/%DO class is very large, containing many billions of characters or bytes.  The %SDC classes contain readonly data so you cannot modify the string data that they contain.  However, you can create any other object in %Stream package of classes that supports the CopyFrom() method (such the %Stream.TmpCharacter, %Stream.TmpBinary, %Stream.FileCharacter or %Stream.FileBinary classes) and use the CopyFrom() method to create a writeable copy of the string data in the %SDC object.  If your %SDC stream contains many billions of data elements then the
    DO tmpStream.CopyFrom(sdc)
access will take much longer to load the tmpStream object than it took to create the original sdc object.

A %DA/%DO object internally contains a data structure called a Packed Vector Array (PVA).  The PVA supports rapid creation from JSON text and also rapid data lookup.  It does not support rapid data modification, although the %Set() method can be used to modify and rearrange the data in a PVA.  When a %DA/%DO contains a string element longer than a selected length (currently defaulting to about 4095 characters) then those characters are placed in a separate buffer object and a small object reference (oref) is placed in the PVA.  The buffer classes are the %DynamicString, %DynamicBinary and %DynamicBase64 classes which are used to contain the characters and bytes of long strings.  These classes are not very interesting to ordinary ObjectScript programers as they have no properties and no methods.  When a %SDC object is created (using something like the SET sdc=dao.%Get(key,,"stream") ObjectScript statement) then the DAOData property in the %SDC object references the buffer class so that characters/bytes in the buffer do not need be copied.  A buffer class can be shared by multiple %DA, %DO, %SDC and %SDB objects, which is why the buffer objects are read only.