ER/Studio - Embarcadero Technologies Product Documentation

USING ER/STUDIO > DEVELOPING THE PHYSICAL MODEL
Name tab
• Should this rollback segment be made public? This option only applies to a database operating in a parallel
server environment. A public rollback segment can be brought online by any instance of the database in a parallel
server environment. A private rollback segment can only be brought online by the database instance that has the
rollback segment specified in its initialization file.
Storage tab
• What extent sizes do you want to assign to this rollback segment?
The before-image details for multiple transactions can be recorded in one rollback segment but each transaction
must fit entirely into one segment and the blocks of a rollback segment are not overwritten until the transaction
that wrote to those blocks has been committed. You must therefore, ensure the rollback segment is big enough
to hold all the information for the longest running query without wrapping and is big enough to hold the undo
information for the largest transaction × number of concurrent transactions ÷ number of rollback segments.
• The default extent size is the size of 5 data blocks. The default minimum extent size is the size of 2 data
blocks. The maximum extent size varies by operating system.
• Optimal Size: The optimal extent size cannot be less that the space initially allocated for the rolback segment.
• What are the minimum and maximum number of extents...?The default minimum number of extents is 2.The
default maximum number of extents varies by operating system.
Definition tab
DDL tab
Enter or edit a definition for the rollback segment. If the target database supports it, ER/Studio adds this
definition as a comment when generating SQL code.
Displays the CREATE ROLLBACK SEGMENT statement needed to build the rollback segment. ER/Studio uses the
platform-specific parser of the model’s selected database platform to generate the rollback segment.
Attachment Bindings tab
Bind an external piece of information, or attachment to the rollback segment. You can also remove an
attachment from an object, override an attachment binding’s default value, or change the position of a bound
attachment. To override the value of the attachment you have moved to the Selected Attachments grid,
double-click the Value field of the target attachment. ER/Studio opens the Value Override Editor or a list
depending on the attachment datatype. Attachments are created in the Attachments folder of the Data Dictionary.
For more information, see Attaching External Documents to the Data Model.
Creating and Editing Sequences
Sequences are used to generate a series of integer values according to rules defined in the sequence. Database
sequences are generally are used to create primary keys; they can also be used to generate random numbers.
The following database platforms support sequences:
• IBM DB2 for LUW 9.x
• Oracle 8.x, 9i, 9i, 10g, and 11g
NOTE: The Sequence Wizard and Sequence Editor share the same options, except for Attachment
Bindings options which are present only in the editor.
EMBARCADERO TECHNOLOGIES > ER/STUDIO® 8.0.3 USER GUIDE 202