Disk space is not a factor, as we are a smaller shop and disk space comes
cheap. However, one thing I did notice is when I increased the modulus to a
very large
number which then increased my disk space to about 3-4x of my record data, my
SELECT queries were slower.
Are the 2 factors when choosing HOW the file is used based on whether your
using?
1) a lot of SELECTS (then looping through the records)
2) grabbing individual records (not using a SELECT)
With this file we really do a lot of SELECTS (option 1), then loop through the
records. With that being said and based on the reading I've done here it would
appear it's better to have a little overflow
and not use up so much disk space for modulus (groups) for this application
since we do use a lot of SELECT queries. Is this correct?
Most of my records are ~ 250 bytes, there's a handful that are 'up to 512
bytes'.
It would seem to me that I would want to REDUCE my split to ~70% to reduce
overflow, and maybe increase my MINIMUM.MODULUS to a # a little bit bigger than
my current modulus (~10% bigger) since this
will be a growing file and will never merge. In my case using the formula might
not make sense since this file will never merge. Does this make sense?
----
File name .................. GENACCTRN_POSTED
Pathname ................... GENACCTRN_POSTED
File type .................. DYNAMIC
File style and revision .... 32BIT Revision 12
Hashing Algorithm .......... GENERAL
No. of groups (modulus) .... 92903 current ( minimum 31, 87 empty,
28248 overflowed, 2510 badly )
Number of records .......... 1292377
Large record size .......... 3267 bytes
Number of large records .... 180
Group size ................. 4096 bytes
Load factors ............... 80% (split), 50% (merge) and 80% (actual)
Total size ................. 501219328 bytes
Total size of record data .. 287426366 bytes
Total size of record IDs ... 21539682 bytes
Unused space ............... 192245088 bytes
Total space for records .... 501211136 bytes
----
With all that being said if I change the following:
1) SPLIT.LOAD to 70%
2) MINIMUM.MODULUS > 130,000
That's all I should really need to do to 'tweak' the performance of this file..
If this doesn't sound right I would be interested to hear how it should be
tweaked instead. Thanks for all the help so far, I think
this is all starting to make sense.
Chris
> From: ro...@stamina.com.au
> To: u2-users@listserver.u2ug.org
> Date: Wed, 4 Jul 2012 01:36:26 +0000
> Subject: Re: [U2] RESIZE - dynamic files
>
> I would suggest that then actual goal is to achieve maximum performance for
> your system, so knowing HOW the file is used on a daily basis can also
> influence decisions. Disk is a cheap commodity, so having some "wastage" in
> file utilization shouldn't factor.
>
>
> Ross Ferris
> Stamina Software
> Visage > Better by Design!
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