Oracle7 Server Distributed Systems Volume II: Replicated Data

Append Site Name/Append Sequence Uniqueness Conflict Resolution Methods

The append site name and append sequence routines work by appending a string to a column that is generating a DUP_VAL_ON_INDEX exception. Although this allows the column to be inserted or updated without violating a unique integrity constraint, it does not provide any form of convergence between multiple master sites. The resulting discrepancies must be manually resolved; therefore, these methods are meant to be used with some form of a notification facility (see Conflict Notification

). Both append site name and append sequence can be used on character columns only.

These methods can be useful when the availability of the data may be more important than the complete accuracy of the data. To allow data to be available as soon as it is replicated

select append site name or append sequence

use a notification scheme to alert the appropriate person to resolve the duplication, instead of logging a conflict

When a uniqueness conflict occurs, the append site name routine appends the global database name of the site originating the transaction to the replicated column value. The name is appended to the first period (.). For example, HOUSTON.WORLD becomes HOUSTON.

Note: Similarly, the append sequence routine appends a generated sequence number to the column value. The column value is truncated as needed. If the generated portion of the column value exceeds the column length, the conflict routine does not resolve the error.