ABAP_to_the_Future

14
Shared Memory
IF sy-subrc <> 0.
"At least remove the material on this server
CALL FUNCTION 'ZMM_SHM_INVALIDATE_MATERIAL'
EXPORTING
id_material = i_mara_new-matnr.
CONTINUE.
ENDIF.
ENDLOOP."Application Servers
Listing 14.9 User Exit on Material Save
The code in Listing 14.9 finds all the ap plication servers on the system and then
loops through them, each time performing an RFC to tell the application server to
update the shared memory object. If the program gets into trouble deleting a single
record, then it invalidates the whole area. In this way, the program can ensure
that when a record is changed, the change is propagated to all application servers.
Once again, this code does not directly change the data; it only deletes a record so
that it gets reloaded on the next read request.
Note
Cynics will still say that you’re going through a lot of effort to manually replicate what
SAP does in the normal course of events for buffered tables, which is why buffering
tables is still the preferred option if possible. Nonetheless, there are some situations
where table buffering just does not cut the mustard and shared memory neatly fills that
gap. (You will also notice that if there is some sort of massive system failure, then the
propagation will not work—but in such an event, this would be the least of your worries.)
You may recall that in Section 2.10 of Chapter 2 we talked about a new feature in
ABAP 7.4 called ABAP Messaging Channels, which sends messages between
application servers. This facility would seem ideally suited to shared objects,
because the object instances on the appl ication servers could send messages to
each other whenever one of them has i ts data changed. You would most likely
still want to delete the records in the other servers.
14.4.2 Short Dumps
When you use a new technology and ge t unexplained short dumps all over the
place, it can put you off in a hurry. All of the examples in this chapter have been
following the SAP party line, and when they cannot instantly attach a shared
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