Performance Considerations

The relative performance speed of APPC/MVS callable services varies depending on the functions that the callable service performs. For example, services that call VTAM or cause the movement of data buffers involve a greater number of internal instructions. For an overview of performance considerations for calls to CPI Communications, see Table 1. For a similar chart of performance considerations for the MVS TP services, see Table 1.

Table 1. Performance Considerations for APPC/MVS CPI Communications Calls
CPI Call	Calls VTAM	Causes DASD I/O	Causes buffer moves	Calls RACF	Creates SMF record
CMINIT	No	Sometimes(1)	No	Sometimes(3)	No
CMALLC	Yes	No	No	RACROUTE= TOKENXTR, TOKENMAP	No
CMCFM	Yes	No	No	No	No
CMCFMD	Yes	No	No	No	No
CMDEAL	Yes	No	No	No	No
CMFLUS	Yes	No	No	No	No
CMACCP	No	No	No	No	No
CMECS	No	No	No	No	No
CMECT	No	No	No	No	No
CMEMN	No	No	No	No	No
CMEPLN	No	No	No	No	No
CMESL	No	No	No	No	No
CMPTR	Yes	No	No	No	No
CMRCV	Yes	No	Yes	No	No
CMRTS	Yes	No	No	No	No
CMSEND	Yes	No	Yes	No	No
CMSERR	Yes	No	No	No	No
CMSCT	No	No	No	No	No
CMSxxx(2)	No	No	No	No	No
Note: Might read from the side information file. (Entries are cached for quick retrieval after first reference). All other CPI Communications Set_xxx calls. Calls RACF only to verify access to side information file.