> -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of Paul Gilmartin > Sent: Sunday, January 15, 2017 9:41 AM > To: [email protected] > Subject: Re: Friday SDB puzzle <snip>
> Pondering this, it occurs to me that given 3390 track size and RECFM=FB, SDB > will always select a BLKSIZE that gives either a prime number of blocks per > track > or one block per track. Once your LRECL is below 18453, any composite (non-prime) block count can be improved by simply multiplying the block size by one of the composite's prime factors and dividing the block count by the same value. If the result is still a composite, repeat. For example, LRECL= 10797 will get the maximum four records per track at BLKSZ=10797. Performing the arithmetic and you get the same four records at BLKSIZE=21594 with the additional advantages of less blocks per track. LRECL=8906 gets the maximum six blocks per track at BLKSZ=8906 but does "better" at BLKSIZE=17812 (3 blocks/track) best at BLKSZ=26718 (2 blocks/track). ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
