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Extension Columns

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Extension columns have a value of Extension in their Type property.

NOTE:  Always use extension columns. Do not use Siebel-defined columns for other purposes even if they seem to be unused.

An extension column is a column that is not used by standard Siebel applications. There are three kinds of extension columns:

• Standard extension columns. Extension columns are include in extension tables for developer use. They are named ATTRIB_nn, where nn is a value between 01 and 47 (for example, ATTRIB_13).
• Custom extension columns in an extension table. These are columns added by the developer to an extension table. They have the prefix X_ in their names.
• Custom extension columns in a base table. These are columns added by the developer to a base table. The relational database system that you use with Siebel applications determines whether or not this is allowed. When the database system supports custom extension columns in base tables, it may be preferable for performance reasons to add them there, rather than to an extension table. Performance may be affected if the extension columns are added to an extension table, because extra SQL is generated to join to the extension table.

Standard Extension Columns

Each extension table provided with Siebel applications includes standard extension columns of various data types. Table 11 lists the different data types found in Siebel extension tables and the number of columns of each data type. These columns are named ATTRIB_nn, where nn is a value from 01 to 47.

Table 11.  Standard Extension Columns 

Data Type	Number of Columns
Number	12
Date	10
VarChar(255) VarChar(100)	1 5
VarChar(50)	10
VarChar(30)	5
Char(1)	4

NOTE:  Extension columns with a Physical Type of VarChar have a text length limit of 2000.

The benefit of using standard extension columns is that they provide the means to add fields to business components for new functionality with a minimum of effort and database impact. If there is a need for a custom column, you can adapt an existing standard extension column in an existing standard extension table without adding any new columns to the database schema.

However, the standard Siebel applications use certain columns in extension tables. The following columns in these tables are used:

• S_CONTACT_X. ATTRIB_03, 04, 05, 06, 07, 08, 14, 15, 26, 48, and MODIFICATION_NUM.
• S_EMPLOYEE_X. ATTRIB_48.
• S_OPTY_X. ATTRIB_04, 05, 08, 09, 10, 11, 15, 16, 17, 18, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45.
• S_ORG_EXT_X. ATTRIB_01, 02, 03, 08, 14, 15, 16, 27, 48, 49, 50, 51, 52, 53.

NOTE:  Extension columns used by standard Siebel applications should be treated as data columns in base tables—that is, they should not be modified or deleted.

Extension Columns and Foreign Keys

Use caution when configuring a standard extension column to hold foreign keys; generally you should avoid the practice. Foreign key extension columns can be appropriate when pointing to enterprise-visible business objects, but not when pointing to limited-visibility business objects such as Opportunity, Contact, Account, or Service Request.

Foreign key relationships based on extension columns in the limited-visibility situation can cause some users not to receive the record, causing the loss of the relationship for all users.

For example, a foreign key may be set to 'No Match Row Id' if Siebel is unable to find the parent record that the foreign key is pointing to. Such cases could arise when you have a limited-visibility business object routed to a mobile user based on a set of visibility rules. As not all records are routed to a local database, your client might end up with a situation where there is a record with a Primary Id Field (for example, on a Multi Value Link) pointing to a record not present on their local database. In such cases, Siebel sets this field to 'No Match Row Id'. Subsequently, when the user synchs up with the server, this Primary Id Field will be set to 'No Match Row Id' for all users on the server. Also, business objects can change from enterprise-visible to limited-visibility with a new release of Siebel applications.

You will also need the assistance of Siebel Expert Services to configure EIM to import data into a foreign key column, because the necessary EIM object types are not customer-configurable. For more information on using EIM to populate foreign key columns, see EIM Interface Tables.

If in doubt, avoid configuring extension columns as foreign key columns.

NOTE:  Do not define columns with names longer than 18 characters in the DB2 environment.

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