Change commands are statements that can be issued against
a DB2 database. Change commands are the central resource for managing change
with DB2® Change Management Expert. They
can be SQL, DB2 commands, or utility commands (such as export and import commands).
Change commands can be generated between the base model and the target
model, manually created, or imported from a script file. DB2 Change Management Expert allows
the SQL, DB2 commands, or utility commands to all be specified in a single
script file.
DB2 Change Management Expert checks
the syntax of change commands in the Change Command Editor. A change command
can be invalid. Change commands are generated based on a particular database
state. If these change commands are applied to the database in a different
state, semantic errors can occur.
DB2 Change Management Expert checks
the semantics of the change command when the change commands are applied to
the model. Error messages are generated if a change command has put the
DB2 Change Management Expert model in an invalid
state.
DB2 Change Management Expert cannot
issue change commands that are not syntactically correct.
DB2 Change Management Expert can
issue commands that might be invalid for semantic reasons; however, proper
use of the deployment script will help to prevent this possibility.
Tip: There
are a variety of editors avail in the Eclipse environment to help you edit
SQL, however the Change Command Editor is probably the best to use when you
are using DB2 Change Management Expert because
it supports syntax checking for all of the commands that DB2 Change Management Expert supports.
Other editors might not support all of the commands or might not check your
syntax. You can specify the default editor based on your file extensions by
selecting . You should use the Change Command
Editor as the default editor for *.chx, *.ddl, and *.sql files.
In addition, DB2 Change Management Expert provides
the Generate Change Commands wizard that generates your change commands for
you. For example, you can manipulate export and import utility commands by
using the DB2 Change Management Expert Generate
Change Commands wizard.
You use change commands to change your target database. You create a deployment
script, which includes all of your change commands, to deploy your changes
to the DB2 catalog. DB2 Change Management Expert automatically
determines how to issue those changes.
A change command that is applied against a DB2 Change Management Expert model
might succeed, but the same command issued against DB2 might fail. DB2 Change Management Expert can be more forgiving
than DB2 because DB2 Change Management Expert shows
you the proposed model of the database and you can decide if the actions taken
by DB2 Change Management Expert were
appropriate. For example, if between the time that you generate change commands
and the time that you deploy them, the DB2 catalog might have changed underneath.
Although the change commands that you applied to the model were successful,
the change commands might fail when you deploy them to DB2 if the base catalog
has been altered.
Tip: The Deployment wizard will warn you of situations where your
commands might fail or if there is a conflict with the database catalog. You
can refresh your base model before you deploy your changes. If a difference
between your base model and the DB2 catalog was found, you must regenerate
your change commands.