This chapter describes Ingres Replicator maintenance options available using Visual DBA, Replicator Manager and the command line interface.
These maintenance options include:
|
|
|
The tasks to be performed when you create or maintain your replicated system include stabilizing the system, copying data into a replicated table, and removing replication objects.
|
|
|
To perform Ingres Replicator maintenance, your system must be in a stable state. To achieve system stability, perform these steps:
Note: Emptying the server queues is a way to keep replicated databases consistent. To verify that the databases are consistent, run an Integrity Report against tables and databases that are in question. For more information, see Table Integrity Report Window.
|
|
|
You can use the copy statement to copy data into an existing replicated table. However, note that using bulk copy bypasses the Change Recorder; therefore, rows added to a table with bulk copy are not replicated.
Note: Normally this does not be a problem because replicated tables have a unique primary or secondary index, and bulk copy does not occur if an index exists.
The Import Assistant also uses the Ingres copy statement to copy data into a table. Hence, the above statement is valid for this application, and rows imported through the Import Assistant cannot be replicated.
For more information, see the section Bulk Copying in the SQL Reference Guide.
Visual DBA: For step-by-step procedures, see the online help topic, Copying Database Objects.
Replicator Manager and Command Line: If bulk copying is used to copy data into a replicated table, use the CreateKeys operation (BothQueue&ShadowTable menu item) to propagate the new data that bypassed normal data capture.
Note: If the table was not empty, this procedure causes collisions.
For more information, see Creation of Replication Keys and CreateKeys Option.
|
|
|
Certain SQL statements can have unexpected effects on replicated tables. Be aware of the following statements when maintaining the replication system:
|
|
|
The SQL statement "modify to truncated" bypasses change recording and, therefore, must not be used with replicated tables. If you are deleting in bulk from a replicated table and the deletion of records is expected to be replicated throughout the replication system, use the delete statement instead of the modify to truncated statement.
Use a modify to truncated statement if you are completely cleaning out a table. In this case, issue modify to truncated on the table to be cleared in every database in the replicated system. It is also recommended that you run the Arcclean utility at this time.
|
|
|
Ingres constraints, which are defined using the create table and alter table statements, must be identical among replicated databases. If the statements are not identical, a Replicator Server transmission error can result. The error occurs when a server is attempting to replicate data into a target database and finds that this violates the constraints of the target database.
In addition, keep in mind that referential integrity constraints cause irresolvable situations if rows related by the constraint are updated on different databases. For example, if a user deletes a customer information row in one database, while another user adds a purchase order for that customer in a second database, and there is a constraint on the purchase order table to the customer table primary key, the purchase order cannot be propagated to the first database. Because this is not a conflict between the same row in the two databases, automatic collision resolution cannot correct this.
The create integrity statement, which is used to define integrity constraints, must also be identical among replicated databases.
|
|
|
If replication is no longer required on a database, the Ingres Replicator database objects (queues and support tables, events, and database procedures) can be removed from a replicated database.
Visual DBA: You remove replication objects by choosing the Dereplicate command from the Operations menu. For more information, see the online help topic Removing Replication Objects.
Command Line: Use the dereplic command to remove Ingres Replicator objects. For more information, see the Command Reference Guide.