ECBs versus RPL exit routines

If asynchronous operations are requested, each macroinstruction can specify that VTAM® do either of two things when the operation is completed: post an ECB or schedule an RPL exit routine.

Here is an example of a SEND macroinstruction that specifies that an ECB be posted upon completion: 
SEND  RPL=(2),AREA=AREA1,STYPE=REQ,RESPOND=(NEX,FME),         C
      OPTCD=ASY,POST=RESP,ECB=ECB1

Figure 1 shows the sequence of events that might occur following the issuance of this macroinstruction.

Here is an example of a SEND macroinstruction that specifies that an RPL exit routine be scheduled upon completion: 
SEND  RPL=(2),AREA=AREA1,STYPE=REQ,RESPOND=(NEX,FME),         C
      OPTCD=ASY,POST=RESP,EXIT=RPLEXIT

Figure 2 shows the sequence of events that might occur following the issuance of this macroinstruction.

Figure 1. General sequence of events when ECB-posting is specified
A diagram shows the sequence of events that might occur following the issuance of a SEND macroinstruction that specifies that an ECB be posted upon completion.
Figure 2. General sequence of events when an RPL exit routine is specified
A diagram shows the sequence of events that might occur following the issuance of a SEND macroinstruction that specifies that an RPL exit routine be scheduled upon completion.