Chris, This is why file-sizing is something that requires careful thought. As some of the other responders have indicated, sometimes you want to keep overflow to a minimum (because accessing individual records that are in overflow takes extra disk reads, which slow down your system, and adding new records to a group that is already in overflow will inevitably be slower than adding a new record to a group which is not in overflow), and sometimes you don't (eg if you have a file that is primarily read in a sequential fashion where you do a Basic SELECT, and then loop through the file reading every single record). Because most of the files that I have supported in my career have been read and written primarily as single-record reads, I have always chosen to minimize overflow as my default criteria, and only sized things for sequential reads when the file is rarely written, rarely read as anything but a 'read them all in no particular order' fashion, and that happens rarely in my experience. However, as other responders have written, 'your mileage may vary'!
Look at how the file is used. Look at what resources you have. Then decide... Susan M. Lynch F. W. Davison & Company, Inc. -----Original Message----- From: u2-users-boun...@listserver.u2ug.org [mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of Chris Austin Sent: 07/03/2012 5:38 PM To: u2-users@listserver.u2ug.org Subject: Re: [U2] RESIZE - dynamic files This is why I'm confused.. Is the goal here to reduce 'overflow' or to keep the 'Total size' of the disk down? If the goal is to keep the total disk size down then it would appear you would want your actual load % a lot higher than 37%.. and then ignore 'some' of the overflow.. Chris > But the total size of your file is up 60%. Reading in 60% more records in a full select of the file is going to be much slower than a few more overflows. > > > -----Original Message----- > From: u2-users-boun...@listserver.u2ug.org [mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of Chris Austin > Sent: Tuesday, July 03, 2012 2:15 PM > To: u2-users@listserver.u2ug.org > Subject: Re: [U2] RESIZE - dynamic files > > > Dan, > > I changed the MINIMUM.MODULUS to the value of 200003 as you suggested and my Actual Load has really gone down (as well as overflow). See below for the results: > > File name .................. GENACCTRN_POSTED > Pathname ................... GENACCTRN_POSTED > File type .................. DYNAMIC > File style and revision .... 32BIT Revision 12 > Hashing Algorithm .......... GENERAL > No. of groups (modulus) .... 200003 current ( minimum 200003, 5263 empty, > 3957 overflowed, 207 badly ) > Number of records .......... 1290469 > Large record size .......... 3267 bytes > Number of large records .... 180 > Group size ................. 4096 bytes > Load factors ............... 90% (split), 50% (merge) and 37% (actual) > Total size ................. 836235264 bytes > Total size of record data .. 287394719 bytes > Total size of record IDs ... 21508521 bytes > Unused space ............... 527323832 bytes > Total space for records .... 836227072 bytes > > My overflow is now @ 2% > My Load is @ 37% (actual) > > granted my empty groups are now up to almost 3% but I hope that won't be a big factor. How does this look? > > Chris _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users
