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Oracle Distributed Systems by Charles Dye

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Column Groups and Priority Groups

Column groups and priority groups provide interfaces to a variety of built-in conflict resolution techniques and the easiest way to configure your application to resolve conflicts automatically. Let’s look at them one at a time.

Column Groups

A column group is a set of one or more columns associated with a single conflict resolution method. A column cannot belong to more than one column group, and columns that are not explicitly assigned to a column group are members of a shadow column group, which Oracle creates by default and which uses the default conflict resolution methods.

For example, suppose that you want to define a column group for the EMPLOYEES table described in the following table:

Column Name

Type

EMPLOYEE_ID

NUMBER(10)

LAST_NAME

VARCHAR2(30)

FIRST_NAME

VARCHAR2(20)

SOCIAL_SECURITY_NO

VARCHAR2(11)

MARITAL_STATUS

VARCHAR2(1)

HOME_PHONE

VARCHAR2(12)

PERS_GLOBAL_NAME

VARCHAR2(30)

PERS_TIMESTAMP

DATE

MANAGER

NUMBER(3)

DEPT

NUMBER(3)

SAL_GRADE

NUMBER(3)

SENIORITY

VARCHAR2(10)

PAYROLL_GLOBAL_NAME

VARCHAR2(30)

PAYROLL_TIMESTAMP

DATE

Use the procedure DBMS_REPCAT.MAKE_COLUMN_GROUP to define a column group for fields that the personnel site maintains (i.e., LAST_NAME, FIRST_NAME, SOCIAL_SECURITY_NO, MARITAL_STATUS, HOME_PHONE). The application records information about changes to these fields in PERS_GLOBAL_NAME and PERS_TIMESTAMP.

EXECUTE dbms_repcat.make_column_group( - gname => 'HR', - oname => 'EMPLOYEES', - column_group => 'CG_EMP_PERSONNEL', - list_of_column_names => ...

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