Gilbert Saint-Flour wrote: > Mike Wood said : >>>>> check the value of DCBTIOT which is increased each time QSAM/BSAM >>>>> start to read the next concatenated DD > >>>> Considering the future, and, hopefully, EAV being more prevalent >>>> in future, a better choice than DCBTIOT is to use DSABTIOT. > >>> Is that due to EAV, or rather XTIOT? > >> Dynamic allocation options that can be exploited based on new option in R12 > > Are you saying that in z/OS R12, DCBTIOT may no longer be updated when > GET/READ switches to the next DD in a concatenation ? In the past 35 years, > to detect this type of situation in my programs, I used the fact that DCBTIOT > is updated. If it no longer happens, it would be a surprise !
Hmmm, well, I still use code which searches the TIOT the old-fashioned way, and if a DD is not found then it is assumed to not be allocated. If XTIOT catches on in a big way, this could be a problem too. Still, if we remember that XTIOT is a feature of dynamic allocation, then (a) JCL DD statement allocations will use the TIOT and not the XTIOT, and (b) if your program does the dynamic allocation then you control if the XTIOT is used or not. Also, it is safe to say DCBTIOT will still be maintained as expected when the allocation uses the TIOT. But, you can see that since the virtual storage address of an XTIOT entry can be more than a GB away from the start of the TIOT, the 2-byte DCBTIOT "TIOT offset" field cannot be maintained as we are used to when the relevant file uses the XTIOT. I guess I better stick to writing batch programs... :) Cheers, Greg ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
