It's not very clear what the actual question is here. I suspect it is for JCL like this --
//A EXEC PGM=---
//ADS DD DISP=(NEW,PASS),UNIT=SYSDA,SPACE=(TRK,(1,1)),...
//B EXEC PGM=---
//ADS DD DISP=(OLD,PASS),DSN=*.A.ADS
//C EXEC PGM=---
//ADS DD DISP=OLD,DSN=*.A.ADS
The answer is the DISP in the third step is identical to the default DISP in the first step. In this case, since the first step specified DISP=NEW, its default is DISP=(NEW,DELETE), so the effective DISP in the third step is DISP=(OLD,DELETE). The same rule applies whether the data set is temporary, which is sort of implied by my JCL, or if a "permanent" data set name is specified in the DD statement in step A. You can find this in the JCL manual much more quickly than asking it here.