I'm beginning the push at our company to look at running 
postgreSQL in production here.  We have a dual CPU 2.8 GHZ Xeon 
Box running oracle.  Typical CPU load runs between 20% and 90%.
Raw DB size is about 200GB.  We hit the disk at roughly 15MB/s
read volume and 3MB/s write.
        At any given time we have from 2 to 70 sessions running
on the instance.  Sessions often persist for 24 hours or more.

                  Total          Free    Free
                  Mb           Mb          %
 IDXS_EXT10     2000        290          14.5   
 DATA_EXT100    10000   3200     32     
 SYSTEM               220             95.2       43.3
 IDXS_EXT100    20000   9600     48
 DATA_EXT10     6000          2990       49.8
 UNDOB                4000      2561.1 64
 TEMP           8000          5802.9 72.5       
 DATA_LOB_EXT20         2000          1560       78
 IDXS_EXT1      500           401        80.2
 DATA_EXT1      4000          3758       94
Total Instance  56720   30258.2         53.3     

There are some immediate questions from our engineers about performance

"- Oracle has one particular performance enhancement that Postgres is
missing.  If you do a select that returns 100,000 rows in a given order,
and all you want are rows 99101 to 99200, then Oracle can do that very
efficiently.  With Postgres, it has to read the first 99200 rows and
then discard the first 99100.  But...  If we really want to look at
performance, then we ought to put together a set of benchmarks of some
typical tasks."

Is this accurate:
accoring to
  -- " The rows skipped by an OFFSET clause still have to be computed 
inside the server; therefore a large OFFSET can be inefficient."

What are the key performance areas I should be looking at?
Where is psql not appropriate to replace Oracle?

Thanks in advance, apologies if this occurs as spam, please send
Replies to me off-list.  

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