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Facilidade de uso
Using HP SHADOWBASE COMPARE
Compare Runs with Running Production Applications
COMPARE can handle that situation very well. During compares HP
SHADOWBASE COMPARE never locks any records of your source or target
table, so your production environment will not be disturbed by locked records.
Because HP SHADOWBASE COMPARE may have to read a large portion or
even all records of your database, some system resources will be used by the
tool.
In a production environment, it may happen that some records of source and
target tables are different only for a short period of time. This can happen
especially in data replication scenarios: replicated data may be “on the fly”
meaning a change was already applied to the source table but not yet on the
target table. If HP SHADOWBASE COMPARE compares source and target
records in such a situation, it will find a difference. A short time later this
difference may have vanished. To handle situations like that, HP
SHADOWBASE COMPARE can use a special iteration technique. This works
as follows: In the first step HP SHADOWBASE COMPARE walks through all
records to compare and looks for differences. If a difference is found, it writes
a record in a specially created difference table. This difference table contains
only the primary key of those records where a difference was found. As soon
as the tool is finished with the first step it starts again, but looks only at the
records contained in the difference table. Typically this number may be very
small compared to the size of the original compare run. If HP SHADOWBASE
COMPARE now finds that the previously found difference is gone, it will delete
the record from the difference table. When it has checked all records in the
difference table, it can start again for those records which still have
differences. This iteration can be repeated as often as required. In each step
the number of remaining differences will become smaller (or stay equal). After
a reasonable number of iterations one can assume that the differences that
are still in the difference table will not be caused by “on the fly” data but will
instead be “real” differences.
The ITERATE command specifies, how many of those iteration steps will be
performed. If this command is not given, or if it is set equal to 0, no extra
iterations beyond the first walk through of the tables will be done and no
difference records will be written.
With HP SHADOWBASE COMPARE it is possible to list only those differences
that were found in a specific iteration step (see the Chapter 4).
In the following example we demonstrate, how the iterations work. During the
second iteration we first delete all rows of the source and then insert into the
source all records of the target, so both tables become equal. To reproduce
these results you will need a second terminal or second terminal window
where you can execute the SQLCI commands given here.
COMPARE>source $data02.yyydema0.exam11
COMPARE>target $data02.yyydema0.exam12
COMPARE>checkpoint 500
COMPARE>iterate 6
COMPARE>save my-third-run
RUN my-third-run saved.
COMPARE>start
---> Target record not found for
HP Shadowbase Compare for SQL—785435-002
39
... Este manual também é adequado para os modelos :
Computadores - HP Integrity NonStop J-Series (596.83 kb)