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UA Scale and Precision Maximum Value
 Technote (FAQ)
 
Question
How to set maximum-size when using scale and precision in the UA.
 
Cause
UA6.2 User's Guide states

"To enable this capability(floating ppint numbers), specify SCALE{<nn>} PRECISION{<mm>} to the right of an attribute definition.
 
For example,                          
FloatAttr1 C 999999 SCALE{2} PRECISION {5} SCALE and PRECISION parameter values must be enclosed inside curly braces.                                                                 
                                                                        
IMPORTANT NOTE: To ensure correct scaling results, you must set the Maximum Size in metafiles for numeric types as greater than 32,767 (32K). 

For example,                                                     
FloatAttr2 C 99999 SCALE{1} PRECISION{5}                                
                                                                        
Otherwise, data values are displayed incorrectly in the portal. Alternatively, you may choose to specify SCALE{<nn>} PRECISION{<mm>} in a derived attribute.

For example,                                       
PktReceivedPerSec C 1000000                                             
PktDiscardedPerSec C 1000000                                            
DiscardedRatio (PktDiscardedPerSec / PktReceivedPerSec) SCALE{3} PRECISION{6}                                                           
The maximum allowed SCALE value is 10 and the maximum allowed PRECISION value is 12. However, when set FloatValue C 99999 SCALE{3} PRECISION{5}

For values less than 10000, the monitoring result is correct. For values larger than 9999, the value is wrong.                        
11111       | 1111.000                                                  
99999       | 9999.000                                                  

It seems 9999.999 is the largest value for this metafile, but actually, the maximum -size is set to 99999.
 
Answer
The maximum size value declared for a Counter or Gauge type           
IntValue1 C 9999        <-- will handle integer 0..9999                 
IntValue2 C 32767       <-- will handle integer 0..32767                
IntValue3 C 32768       <-- will handle integer 0..32768                
IntValue4 C 99999       <-- will handle integer 0..99999                

Now, there is an important threshold for maximum size value when you introduce SCALE feature, for supporting and formatting floating point numbers.                                           
IntValue2 C 32767       <- internal type is a short,16 bit int         
IntValue3 C 32768       <- internal type is a long,32 bit int         

So, if I declare ...                                         
FltValue1 C 32767 SCALE{2} PRECISIO {7} let's use a example raw data value received by UA to 327.68.                        
UA code will take raw data value and in this case apply a SCALE of 2, so we have 327.68 x 100 = 32768  which UA then tries to store in a 2 byte int data type the resulting value will be incorrect.         

RULE #1:                                                                
=========================================================               
Any attribute that declares SCALE must have a maximum size value declared of at least 32768 [ this is because we always need a 32 bit integer type for UA to perform the scaling arithmetic ]  

For example -> FltValue2 C 32768 SCALE{2} PRECISION{7}                                 

This declaration will support values from 0.00 to 32768.00        
      
RULE #2:                                                                
=========================================================               
PRECISION setting must be equal to or greater than the sum ofnumber of digit positions in 'maximum size' value and number of digit positions for declared by SCALE {n} qualifier.       

For example -> FltValue2 C 32768 SCALE{2} PRECISION{7}                                 

we have 5 digit positions per the '32768' and 2 digit positions per SCALE{2}, so 5 + 2 = 7, thus PRECISION must declare at least size of 7. 
                                                         
RULE #3:                                                                
==========================================================              
The 'maximum size' value must be large enough for the largestwhole number portion of the floating point number you wish tomonitor.                                              

For example ->                                           
FltValue2 C 32768 SCALE{2} PRECISION{7}   
will not handle larger than 32768.00                 
                                                            
FltValue2 C 99999 SCALE{2} PRECISION {7}   
will not handle values larger than 99999.00 So for case of customer's data set, per float.txt ...        

float.txt                                                  

string   number                                                         
-------  -------                                                        
1.1111   1.1111                                                         
11.111   11.111                                                         
111.11   111.11                                                         
1111.1   1111.1                                                         
11111    11111                                                          
111111   111111                                                         
9999     9999.000                                                       
9999.9   9999.900                                                       
9999.999 9999.999                                                       
99999    9999.000

- the largest whole number in data set is 111111, so 'maximum size'value must be at least 111111 ( RULE #3 )                            

- digit count for 'maximum size' is 6, digit count for SCALE is 3,so PRECISION will be 6 + 3 = 9  ( RULE #2 )                         

- 'maximum size' value for this data set needs to be at least 111111 which is greater than or equal to 32768  ( RULE #1 )                 
Thus the minimal attribute declaration for the float.txt data set is ...
FltValue C 111111 SCALE{3} PRECISION{9}                                 
Best Practice would advise that one declare ...          
FltValue C 999999 SCALE{3} PRECISION{9}                                 
so as to accommodate the largest value of 10 to the 6th power
 
 
 

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Document information
 Product categories:
 Software
 Systems and Asset Management
 Application Performance & Availability
 IBM Tivoli Monitoring
 Operating system(s):
  AIX, AIX 64bit, HP-UX, Linux, Solaris, Windows
 Software version:
  6.2
 Reference #:
  1322639
 IBM Group:
 Software Group
 Modified date:
 2009-04-01

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