Timestamp-based downloads require a TIMESTAMP column for each synchronized table in the consolidated database to track when changes are made to rows.
The TIMESTAMP column records the last time synchronization changes were made in the consolidated database. This column resides on the consolidated database, and it should never be synchronized or changed by another process.
This page allows you to specify the name of the TIMESTAMP column, and whether the column should be added to synchronized tables or whether shadow tables should be created to hold the timestamp.
This page has the following components:
Timestamp column name Shows the name of the TIMESTAMP column.
Use timestamp columns in synchronized tables Select this option to add TIMESTAMP columns to your synchronized tables on the consolidated database. Choose this option if you are willing to change the consolidated table definition. When you deploy the model, a TIMESTAMP column is added to each synchronized table in the consolidated database if it does not already exist.
If you try to redeploy this model to the consolidated database, you are prompted to update the consolidated schema in the model.
Use a column default instead of a trigger Select this option to use a column default instead of a trigger to maintain the TIMESTAMP column. This option is only available for SQL Anywhere, MySQL and IBM DB2 LUW consolidated databases. Using a column default instead of a trigger can result in better performance when rows are inserted or updated in the consolidated database.
For MySQL and IBM DB2 LUW, only one column in a table can have the required default value so you can only use this option for tables that do not already have such a column, otherwise you have to use the existing column name for TIMESTAMP column name.
Use shadow tables to hold timestamp columns Select this option if you want to create a shadow table for each synchronized consolidated database table. Select this option if you don't want to modify the schema of the synchronized consolidated database by adding TIMESTAMP columns. The shadow tables have two columns, one holding the primary key for the table, and the other holding the timestamp. Shadow tables are created with the same owner as the base table.
You can view and modify these options in the Mappings tab after the Create Synchronization Model Wizard finishes. See Modifying the download type.
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