solidDB Help : Replication : Advanced Replication : Maintaining a distributed system : Upgrading schemas in a distributed system by using Maintenance Mode features : Set catalog sync mode to Maintenance mode
  
Set catalog sync mode to Maintenance mode
To permit schema changes (DDL operations) on tables that are referenced by a publication, without having to drop the publication, you can set the catalog sync mode to Maintenance mode, see SET SYNC MODE.
If the catalog sync mode is not set to Maintenance mode, then the server prohibits DDL operations on tables that are used by publications. To change a table, you have to drop the publication, change the table, re-create the publication (even if the change to the table did not affect the publication), and force replicas to get a full refresh of the data.
Setting the sync mode to Maintenance mode temporarily disables sync history; in other words, the server does not store the data that is used to determine which records to send to a replica database when the replica requests a refresh of the data. You can then make major data changes (DML operations) to the master database, make the same updates to the replica database, and skip the synchronization step.
Note You must be careful when making changes to the master and replica databases when you have the catalog sync mode set to Maintenance mode. if the master and replica databases end up out of sync, the master and replica databases do not automatically resynchronize (correct the error) the next time that the replica database does an incremental refresh, and a full refresh is required.
When you set the sync mode back to Normal mode (the default value), the server resumes tracking sync history information, and stops allowing DDL operations on tables that are referenced by publications.
Note that using this method does not guarantee that a replica database will not require a full refresh of the data. Some changes to a table (for example, dropping a column that is used in a publication) might affect the publication such that the replica databases have to get a full refresh of the data.
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Upgrading schemas in a distributed system by using Maintenance Mode features