Format Pool (LFP) tuning.

, , ,
1

I have done an ADABAS tuning course a couple of years ago. On that course they suggested you should not make the LFP > 1500000 because of the scan mechanisim ADABAS uses to scan the pool. As I said, it was a couple of years ago. We are running V 7.4.3 now. Have they changed the way ADABAS scan the pool? Can we increase the pool size. What is the suggested maximum size (performance wise). Thanks.

2

Hi Kobus,
I do not know how many years ago your training was. I was looking thru my old records; and found out following:

  1. with Version 6.1. the UQE was extended and we keep there an anchor to the private Formatids which are then linked together in the LFP
  2. with Version 6.2. the unused space in the LFP get chained
  3. with Version 7.4.2. there was a zap (AN742192) which is included in 743 where the limitation of 5 Global Format IDs in the UQE was removed, the GFIDs are now also chained in the LFP

All together from the theory the recommendation to limit the LFP to have a better performance do not longer apply to Adabas Version 7.4.3
Unfortunally I cannot tell you about the pratical side - I only saw some Requests where other customers have a value of 5.000.000 for LFP and it seems to work…
Personally I would recommend that you increase the LFP and whatch your performance.
Regards,
Uschi

3

Thanks Ursula. I will play around with the sizes and monitor the performance.

4

Kobus,
I did an extensive study of LFP for the 2004 Boston Natural Conference
(Adaruns as a Sunday class), then modified it this year because of the
zap alluded to above.
If you do not have any Global Format Id’s (most likely a non-Natural
shop), then the LFP should be sized until format overwrites are eliminated.
If you have Natural and/or global format id, there still is a tradeoff
between scanning the global format id chain versus the time it takes
to translate a new gfid ifb (this is analagous to the old Adabas Version 4
discussions). For a database with just global format id’s, the formula
for LFP should be (based on cpu studies of scan time versus translate
time):

LFP = (AVER.IFB.LEN) * N.GFID.IFB

N.GFID.IFB = 2 * 30 * (AVER.FLDS/FB)

AVER.FLDS/FB = FBL / 9

average FBL can be obtained by command log samling.

regards,

jim poole
james.poole@eds.com

5

Thanks Jim for the info. We are a pure NATURAL shop.