How SAS Processes Programs
When you submit a DATA step, SAS processes the DATA step and creates a new SAS data set. A SAS DATA step is processed in two phases:
Figure 7.1 DATA Step Process
When you submit a DATA step for execution, SAS checks the syntax of the SAS statements and compiles them. In this phase, SAS identifies the type and length of each new variable, and determines whether a variable type conversion is necessary for each subsequent reference to a variable. During the compilation phase, SAS creates the following items:
program data vector (PDV)
When the compilation phase is complete, ...