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vignesh subramanian

New User

Joined: 08 May 2009
Posts: 2
Location: Bangalore

 Posted: Thu Jul 09, 2009 1:14 am    Post subject: Calculating space for a PDS with 100 members Hi! A PDS should hold 100 members, each member having a maximum capacity of 50,000 records. Record length is 200 bytes each. what minimum primary, secondary and directory values should be assigned in the SPACE parameter when allocating this PDS? SPACE (CYL,(?,?,?)) Thanks VS

Robert Sample

Global Moderator

Joined: 06 Jun 2008
Posts: 8344
Location: Dubuque, Iowa, USA

 Posted: Thu Jul 09, 2009 1:26 am    Post subject: What did you calculate? ISPF statistics or not?
vignesh subramanian

New User

Joined: 08 May 2009
Posts: 2
Location: Bangalore

 Posted: Thu Jul 09, 2009 1:35 am    Post subject: Reply to: Calculating space for a PDS with 100 members I referred to the last post in the below link to calculate the number of cylinders, but not sure of the value for directory http://www.ibmmainframes.com/about24595.html See my calculation below. 27998 / 200 = 13900, which is the optimum blocksize for a 3390 DASD. This means that we get 139 records per block and two blocks on each track. So 279 records on each track. 50,000 / 279 = 179.21 (rounded up to) 180 tracks of used space. = 18,000 tracks for 100 members 180 / 15 = 12 cylinders of used DASD space. = 1,200 cylinders for 100 members
enrico-sorichetti

Senior Member

Joined: 14 Mar 2007
Posts: 10478
Location: italy

 Posted: Thu Jul 09, 2009 2:19 am    Post subject: Reply to: Calculating space for a PDS with 100 members Your computations ( at least the intermediate steps) are a few bytes off ( even if You get the right results because of rounding ) for 3390 here are the exact figures the best blksize for your case ( LRECL=200 ) is 27800 ( edited to correcta typo ) which gives 2 blocks per track for 278 record per track which for a 50000 records for each member gives 50000 / 278 = 179.8561 tracks which rounded gives 180 tracks for each member or 12 cylinders ( at 15 tracks per cylinder ) which gives 1200 cylinders ( for 100 members ) as far as the directory blocks are concerned ( for a PDS - not a PDSE ) see this post for the computation details http://www.ibmmainframes.com/viewtopic.php?t=29878 with ispf statistics You will need 100/6 ==> 17 directory blocks allocating in cylinders You should specify something along... SPACE=(CYL,(1201,1200,44)) 1 track of directory blocks the secondary allocation is arbitrary, for Your estimates, it allows one edit and replace for each member
expat

Global Moderator

Joined: 14 Mar 2007
Posts: 8686
Location: Back in jolly old England

 Posted: Thu Jul 09, 2009 11:22 am    Post subject: With directory blocks I always do my allocations in tracks. The last track will hold only 44 blocks, where all others 45, so to fully utilise the track I use, 44,89,134,................ starting with 44, and then incrementing by 45
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