Oracle7 Server Distributed Systems Volume II: Replicated Data

Minimum and Maximum Update Conflict Resolution Methods

When the symmetric replication facility detects a conflict with a column group and calls the minimum value conflict resolution routine, it compares the new value from the originating site with the current value from the destination site for a designated column in the column group. You must designate this column when you select the minimum value conflict resolution routine.

If the new value of the designated column is less than the current value, the column group values from the originating site are applied at the destination site (assuming that all other errors were successfully resolved for the row). If the new value of the designated column is greater than the current value, the conflict is resolved by leaving the current values of the column group unchanged.

Note: If the two values for the designated column are the same (for example, if the designated column was not the column causing the conflict), the conflict is not resolved, and the values of the columns in the column group remain unchanged. Designate a backup conflict resolution method to be used in this case.

The maximum value method is the same as the minimum value method, except that the values from the originating site are only applied if the value of the designated column at the originating site is greater than the value of the designated column at the destination site.

There are no restrictions on the datatypes of the columns in the column group. Convergence for more than two master sites is only guaranteed if

for the maximum method, the column value is always increasing

for the minimum method, the column value is always decreasing

Note: You should not enforce an always-increasing restriction by using a check constraint because the constraint could interfere with conflict resolution.