开云体育

Hi :)

Following my first questions about how MVS OS family allocates in integer number of racks,

I am reading But, I find this: """ Reasons for Blocking Records The primary reason for blocking records is to pack direct access storage more efficiently. With blocked records, there is an Address Marker, Count Area, Key Area, and gaps for each block of records rather than for each logical record. Another reason for blocking is that it may save time. If records are processed consecutively, there is only one rotational delay before reading or writing a block of records. If records are not processed consecutively, however, blocking may be a disadvantage, since it takes longer to be processed. """

Is IBM 3390 is a CKD disk? If I allocate a data set with block size 512B, it will be read and written in chunks of 512B at a time? if I give a data set a block size of 4KB, it will be read and written in chunks of 4KB at a time? Do all tracks in a CKD disk have the same amount of bytes? The reason why we need set a BLKSIZE is to make the maximum integer number of those user-defined blocks fit in each track?

Kind Regards Sergio Lindo Mansilla

MVS uses Count Key Data formatted disk. The various device types have
different amounts of bytes that can be written in one track, different
amounts of bytes to skip between blocks, etc. Introduction To The New
Mainframe may be useful to you.


On Fri, Oct 25, 2024 at 5:33?AM Sergio via groups.io
<sergiolindo.empresa@...> wrote:

Hi :)

Following my first questions about how MVS OS family allocates in integer number of racks,

I am reading But, I find this: """ Reasons for Blocking Records The primary reason for blocking records is to pack direct access storage more efficiently. With blocked records, there is an Address Marker, Count Area, Key Area, and gaps for each block of records rather than for each logical record. Another reason for blocking is that it may save time. If records are processed consecutively, there is only one rotational delay before reading or writing a block of records. If records are not processed consecutively, however, blocking may be a disadvantage, since it takes longer to be processed. """

Is IBM 3390 is a CKD disk? If I allocate a data set with block size 512B, it will be read and written in chunks of 512B at a time? if I give a data set a block size of 4KB, it will be read and written in chunks of 4KB at a time? Do all tracks in a CKD disk have the same amount of bytes? The reason why we need set a BLKSIZE is to make the maximum integer number of those user-defined blocks fit in each track?

Kind Regards Sergio Lindo Mansilla

--
Mike A Schwab, Springfield IL USA
Where do Forest Rangers go to get away from it all?