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Siebel Tools Reference > Adding Custom Extensions to the Data Model > Database Extension Planning and Design >
DBMS Restrictions
You can add extension columns to a base table, standard extension table, or custom extension table.
However, you should be aware that different DBMS systems have different limits on the width of a table row, either on the maximum number of columns in a table or the maximum number of bytes in a row. If you need to exceed the limit, you can add extension columns to custom extension tables only. Some examples of DBMS systems limitations are:
- Microsoft SQL Server 7.0 has a maximum Varchar length of 8000.
- Customers cannot add long columns to Siebel tables. However, customers can add one long column to custom extension tables in Oracle.
After it has been added to the physical table, a column cannot be removed. Refer to your database system's documentation for information on this constraint.
NOTE: Customers are advised not to decrease the length of a column because this can cause data loss [for example, decreasing a varchar (30) to varchar (20)] or to decrease the precision [for example, decreasing from number (10,3) to number (10,1)] because this can cause a loss of precision.
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Siebel Tools Reference, Version 7.5, Rev. A Published: 18 April 2003 |