Question: I save a heap of problem with
your
10g upgrade gotchas and I wonder what perils await me as I
prepare to migrate to Oracle 11g?
Answer: There are several 11g upgrade
gotchas, small surprises that can effect your database performance
when you migrate to 11g:
-
Optimizer
enhancements: With each release of Oracle we see
improvements to the SQL optimizer, and you can expect to see
many plan improve, but some which may get worse. Unless
you like surprises, it's an Oracle best practice to "freeze" SQL
execution plans with SQL profiles or Stored Outlines, and
gradually introduce your SQL to the new optimizer.
-
SQL Plan Manager: The 10g SQL profile
approach is deprecated, and the 11g SQL plan management uses
only two parameters, optimizer_capture_sql_plan_baselines
and optimizer_use_sql_plan_baselines.
-
Optimizer statistics: For all indexes
with functions (function-based indexes) make sure to analyze
them with the new 11g
extended optimizer statistics.
-
Double
check your SYSAUX tablespace status: If the
SYSAUX tablespace is offline in 11g, this can cause significant
performance impact because required needed SQL Profiles are not
accessible.
- Resource Manager enables itself: The
Oracle
11g resource manager now turns-on by default. Check
the value of the resource_manager_plan init.ora parameter.
If it is set to DEFAULT_PLAN you may want to change it to a more
appropriate value, or use the following command to disable the
resource manager:
alter system set resource_manager_plan='';
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