IBM Mainframe Forum Index
 
Log In
 
IBM Mainframe Forum Index Mainframe: Search IBM Mainframe Forum: FAQ Register
 

Data set Rec-Cnt and Byte-Cnt


IBM Mainframe Forums -> Testing & Performance
Post new topic   Reply to topic
View previous topic :: View next topic  
Author Message
leoben

New User


Joined: 21 Mar 2023
Posts: 4
Location: United Kingdom

PostPosted: Tue Jan 09, 2024 5:22 pm
Reply with quote

Hi all,

I'm currently trying to wrap my head around how I can accurately calculate the size I need to allocate to a data set when writing output from the spool via the xdc command. My device type is 3390.

The spool output i'm currently working with has the following:

Code:

Rec-Cnt             01  5,183 
Byte-Cnt            01  77,209
LRecL               01  251


When I allocate a data set using KB as my space unit, I get the following:

Code:

Current Allocation
  Allocated kilobytes : 709
  Allocated extents . : 12

 Current Utilization       
  Used kilobytes  . . : 681
  Used extents  . . . : 12


When I switch to tracks, I get the following:

Code:

Current Allocation       
 Allocated tracks  . : 13
 Allocated extents . : 9
                                               
Current Utilization     
 Used tracks . . . . : 13
 Used extents  . . . : 9


Based on some of the reading I've done, each track should be 56664 bytes for a 3390 disk type. The 681 KB thus seems to match up with the 13 tracks (as 12x56664 would not be enough).

Is there anyway I can determine the size i need from the Rec-cnt, Byte-cnt and LREC. Happy to be pointed to any resources, I've just exhausted my own Googling abilities.

Thanks in advance.
Back to top
View user's profile Send private message
sergeyken

Senior Member


Joined: 29 Apr 2008
Posts: 2000
Location: USA

PostPosted: Tue Jan 09, 2024 6:06 pm
Reply with quote

1. The actually used disk space seriously depends on your BLKSIZE. If BLKSIZE is small (e.g. is equal to a single LRECL) then too many interblock gaps do appear along the track, which leads to loose of space. In you situation use BLKSIZE=25100 (for RECFM=FB), or BLKSIZE=25104 (for RECFM=VB), or BLKSIZE=0 (to allow zOS calculate adequate BLKSIZE for you).

2. You can specify required space in terms of bytes you need.
SPACE=(blksize,(primary,secondary),RLSE)
blksize is the physical record = block size in bytes.
Back to top
View user's profile Send private message
Willy Jensen

Active Member


Joined: 01 Sep 2015
Posts: 710
Location: Denmark

PostPosted: Tue Jan 09, 2024 10:13 pm
Reply with quote

I just tried XDC with defaults except from blksize 0, it gave me a dataset allocated as VBA 240 244, which is not good. It might of course be down to the ACS routines at that particular site. Since you say that you are using the SDSF XDC command, I will suggest that you instead allocate with lrecl 27994 and bksize either 0 or 27998. As to the space, try with TRKS 8, 15 and see what happens.
You will probably use the dataset for other output in the future, so just make it big enough.
Back to top
View user's profile Send private message
View previous topic :: :: View next topic  
Post new topic   Reply to topic View Bookmarks
All times are GMT + 6 Hours
Forum Index -> Testing & Performance

 


Similar Topics
Topic Forum Replies
No new posts SCOPE PENDING option -check data DB2 2
No new posts 10 byte RBA conversion DB2 2
No new posts 10 byte RBA conversion -non applicati... JCL & VSAM 1
No new posts Check data with Exception Table DB2 0
No new posts JCL EXEC PARM data in C Java & MQSeries 2
Search our Forums:

Back to Top