The match-merging examples in this chapter are straightforward.
However, match-merging can be more complex, depending on your data
and on the output data set that you want to create. To predict the
results of match-merges correctly, you need to understand how the
DATA step performs match-merges.
When you submit a DATA step, it
is processed in two phases:
the compilation phase, in which
SAS checks the syntax of the SAS statements and compiles them
(translates them into machine code). During this phase, SAS also
sets up descriptor information for the output data set and creates
the program data vector (PDV), an area of memory where SAS holds
one observation at a time.
Match-Merge Processing: Compilation ...