HP 3000 Manuals

ALLBASE/SQL Performance and Monitoring Guidelines

Removing Non-Database Processing from Transactions 

Transactions affect performance because they hold locks until they are
terminated with a COMMIT WORK or ROLLBACK WORK statement.  If the
transaction contains processing that could actually be performed outside
the transaction, this processing takes time, which means that locks may
be held longer than needed, which reduces concurrency and degrades
performance.  Such extra processing should be removed from the
transaction.

Whenever possible, avoid holding locks around terminal reads.  As a
general rule, all user input should be retrieved before the start of the
transaction.  This helps to keep the transaction as short in duration as
possible, and it has the following advantages:

   *   Locks are not held around user prompts, thus avoiding application
       "hangs."

   *   The result of the transaction can be viewed and used by other
       users sooner, thus improving throughput.

When user input must be accepted during a transaction, you can use
ALLBASE/SQL features that help avoid excessive locking.  In cursor
operations, you can use KEEP CURSOR WITH NOLOCKS when reading data.  For
cursor or non-cursor operations, you can use the RC or RU isolation
level.  When using these options, you can use the REFETCH statement to
acquire locks and revalidate data before updating tuples.

MPE/iX 5.0 Documentation