I was trying to find something in the CONTEXT_FILE when I happened to notice the AF_CLASSPATH env variable (not that I haven't noticed it earlier). But this time, it set me thinking as to what might its purpose be since we already had a CLASSPATH variable and its value seemed to be the same as the AF_CLASSPATH variable.
I found 3 variables starting with AF:
I wanted to find out what they were and why they were used.
This is the explanation provided in Metalink Note 412709.1 (Oracle Workflow Documentation Updates for 11i.ATG_PF.H.delta.5 (RUP 5))
AFJVAPRG - The location of the JDK or JRE executable for the concurrent processing tier.
AF_CLASSPATH - The classpath for the concurrent processing tier.
Also, Note 373386.1 has this to say about AF_CLASSPATH.
The AF_CLASSPATH variable is used by JAVA concurrent programs and must use literal (full) path values.
By combining the above two notes, we can perhaps safely say that the AF variables are set for letting programs know the location of java (AFJVAPRG), JRE (AF_JRE_TOP) and the classpath (AF_CLASSPATH) on the concurrent node.
Also, note that these variables are also set on the web node (and must be set to valid values too).