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Message Posted: Tue, 03 Dec 2002 @ 09:43:24 GMT


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Subj:		Re: Sessions vs AMPs vs Data

From:		Matthew Winter

Hi,

> Based on our experience with FastLoads, and attempting to maximise the performance bu minimise the number of sessions, I calculated a formula to work out the number of sessions a FastLoad script should use.

Is following formula is only for FastLoad? IS this applies for MultiLoad and Tpump also?

The formula is just for FastLoad. We do not make use of MultiLoad or TPump.

> 1. Calculate the number of records contained within a message (64K Block). This is output as part of the FastLoad logs. Call this value RM.

I got following message from my Fastload Job output for table1
**** 16:32:29 Number of recs/msg: 690
**** 16:32:29 Starting to send to RDBMS with rec
**** 16:32:29 Sending row 77
**** 16:32:29 Finished sending rows to the RDBMS

Here RM is 690
AM i correct?

Yes, you are correct, RM = 690 for this example.

> 2. Calculate the average number of records for a single load. Call this value AR.

How to calculate this?

Taking the last 5 to 10 loads, total the number of records loaded and divide by the number of load scripts.

Unless you have a very uneven set of load scripts, the above calculation will do. If you do have an uneven set of load scripts, take a set of the max values and calculate the average.

> 3. Calculate the average number of message blocks required to be transferred. Call this value AM, which is calculated as ROUNDUP(AR / RM, 0) within Excel.

How to calculate this without using Excel?

The ROUNDUP function is basic rounding of values, the 0 is for no decimal places. Basically any 2.x values goes up to 3, except 2.0

So for example, if your average number of records is 10,000 with the RM = 690

AR / RM = 10000/690 = 14.49
Therefore AM = 15

> 4. NM = Number of AMPs on your system.

> 5. IF ((AM / 100) is less than NM) THEN Number of Sessions = AM / 100 ELSE Number of Sessions = NM

I hope you find the above useful.

Taking this example further:

AM / 100 = 15 / 100 = 0.15, ROUNDUP = 1
This value would be less than the number of sessions

Therefore for this example I would stick with only a single session.

I have been asked what the 100 signifies.

I calculated for our setup, that on average a single session logon took half a second, in which time on average 120 blocks could be transferred, with a MIN of 80 and MAX of 150. I used 100 as the value, mainly to take a more cautionary route.

The only problem with performing this kind of calculation, is that when you upgrade your system, this value can change. We are going through an upgrade at present, which I expect this value to significantly change, as we are doubling the ESCON capacitiy and dedicated PE's for the Mainframe Load Processes

Remember the above should be used only as a guide and for more accurate results you should calculate the constant for your system.

Regards

Matthew Winter

Technical Architect
TPG IS Design Authority
Teradata Certified Professional


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