1. Why should I use a graphical product over scripts?
  2. Why should I used DB Optimizer over Quest Spotlight?
  3. Why should I used DB Optimizer over Oracle's Enterprise Manager
    • OEM is only one platform Oracle whereas DB Optimizer covers Oracle, Sybase, SQL Server, DB2
    • OEM is first available in 10g, where as DB Optimizer works across Oracle 8,9,10 and 11
    • DB Optimizer is fast more compact where as OEM has 100s of separate pages taking seconds to navigate between
    • DB Optimizer offers finer grain and more flexible aggregate periods from 5 seconds wide, to hours  for top SQL, Session and Event
    • DB Optimizer is much much cheaper than OEM. If you can afford OEM , the DB Optimizer is a great alternative, if you have OEM then DB Optimizer offers a faster, finer grain, more compact interface
    • DB Optimizers Visual SQL Tuning diagrams showing the join tree, table sizes, filter percentages, and join sizes is only available in DB Optimizer
  4. Overhead
    • Inexpensive
    • Platform  specific, for example testing on Oracle it’s less than 1% of one cpu
  5. Speed
    • Fast
    • Sample every second, refresh every 5 seconds
  6. Method
    • Powerful
    • Sample once a second user states and build up a model of load on database.
    • We collect multiple attributes about the active users and the data can be aggregated in different dimensions. We display different dimensions such as top SQL, Event, Session on the database or for a specific session the sessions top sql, the sessions top event, or for a SQL statement the top sessions executing that SQL, the top wait events for the SQL or for an event the top sessions running into that event and the top sql running into that event.
  7. Amount of data
    • Small but concentrated
    • Amount of data depends on the number or active sessions. More active sessions, more data. Less active sessions less data. Typically data is small for example less than 1M for an hour of profiling for 10 active sessions.

SQL shows up as "Unknown"  in profilers Overiew and Top Activity (Oracle)

The UNKNOWN  is one of the  following
  1.   Commit (log file sync)
  2.   non-sql from background processes
  3.   uncollected SQL - we gather SQL text every 15 seconds
  4.   bug(s)
Normally it's 1-3, and you can expand the node and see how much "non-sql" there is which includes commits.
on the other hand I've seen cases where we should have gotten SQL and we didn't.
In DB Optimizer 2.5 we will keep retrying missing SQL text, ie if we don't find it the first collect, we will try again.