What is the meaning of the EXEC statement keyword, COND? What is its syntax?

COND specifies the conditions for executing the subsequent job step. The value after the COND= is compared to the return codes of the preceding steps and if the comparison is true, the step is bypassed. 

In exec statement the condition is used for by-passing the perticular step through the condition
if COND 0 Its a successfull execution
if COND 4 Its a warning
if COND 8 Its a serious error
if COND 16 Its a fatal error.
So that we can use this condition key word.