StatsPack and AWR Reports -- Bits and Pieces -- 1

I am planning to put up a few posts on snippets from StatsPack and AWR reports.  This is my first post.
Note : Some figures / details may be slightly changed / masked to hide the real source.

Logical I/O and Change rates :
1.  From a 9.2 StatsPack Report:

Cache Sizes (end)
~~~~~~~~~~~~~~~~~
               Buffer Cache:                 Std Block Size:          4K
           Shared Pool Size:                     Log Buffer:      

Load Profile
~~~~~~~~~~~~                            Per Second      
                                   ---------------      
                  Redo size:             56,031.63               
              Logical reads:             68,286.24             
              Block changes:                314.88                
             Physical reads:                842.92                 
            Physical writes:                134.76                 

With a 4KB Block Size 68,286.24 Logical Reads translates to slightly over 266MB/second. Logical I/O is CPU-bound.  Database activity is Read-Intensive with a high rate of Reads relative to Writes.

2.  From an 11.2 AWR Report :
Cache Sizes

	Begin	End
Buffer Cache:			Std Block Size:	16K
Shared Pool Size:			Log Buffer:

Load Profile

	Per Second	Per Transaction	Per Exec	Per Call
DB Time(s):
DB CPU(s):
Redo size:	1,593,612.1
Logical reads:	51,872.5
Block changes:	4,212.4
Physical reads:	63.8
Physical writes:	133.1

With a 16KB Block Size, 51,872.5 Logical Reads translates to slightly over 810MB/second.  This consumes CPU cycles.  However, here the number of Block Changes is noticeably high in this environment. This is also reflected in the high Redo rate -- slightly over 5,471MB/hour (Note : "Redo size" is in Bytes).


CPU Consumption :
1.  From a 9.2 StatsPack Report :

Statistic                                      Total     per Second    per Trans
--------------------------------- ------------------ -------------- ------------
CPU used by this session                                       37.5          2.1
CPU used when call started                                     37.6          2.1

This indicates 0.375seconds of CPU usage per second -- i.e. approximately 37.5% of 1 CPU (let's take this as an older non-multicore architecture). If the server has 4 CPUs, CPU consumption is 9.4%

2.  From an 11.2 AWR Report :

Instance Activity Stats

• Ordered by statistic name

Statistic	Total	per Second	per Trans
... deleted rows ....
... deleted rows ....
CPU used by this session		46.85
CPU used when call started		46.27

This indicates 0.468seconds of CPU usage per second -- i.e. approximately 46.8% of 1 Core.  This is also reflected in the Load Profile section :

Load Profile

	Per Second	Per Transaction	Per Exec	Per Call
DB Time(s):
DB CPU(s):	0.5	0.1	0.00	0.00

How many CPUs does this machine have ?  AWR reports this :

Host Name	Platform	CPUs	Cores	Sockets	Memory (GB)
	Linux x86 64-bit	16	16	2

That means we are using less than half of 1 of 16 cores !  This translates to CPU consumption of 3.125%  The server has too many CPU cores !