When you SET SYNC MODE MAINTENANCE in a database, you tell the server not to update synchistory info. Because the server is not recording changes, the next incremental refresh does not necessarily copy all changes from the master to the replica. Before you synchronize the master and replica databases, you must repeat the master database changes in the replica databases. Use the Maintenance Mode in the replica also.
The requirement for applying in both master and replica is an important difference from the way that a solidDB® synchronized system normally behaves. One of the major advantages of the advanced replication technology is that it allows a system to be “self-healing” in some situations. Incorrect data on a replica tends to be replaced with data from the master, and therefore errors on replicas tend to disappear over time.
In Maintenance Mode, however, you lose this self-healing property. Since the master and replica do not store sync history data, they do not know what changes were made, and the master does not send all the updates to the replica the next time that the replica refreshes.
There are two possible sources of error:
1 You might accidentally make a different change on the master than on the replica. For example, when you add a new column to a table, you might set the default value to 1 on the master, but accidentally set it to 2 on the replica.
2 Even if you perform the same operations without error on both the master and the replica, certain types of errors might occur if the replica and master do not have the same starting values of data. For example, imagine that the master and replica each calculate sales tax on an invoice. If the master and replica have different values for the total price on the invoice, they calculate different sales tax, even if they use the same formula. This situation is easy to get into because replicas and masters are updated independently (asynchronously) during Maintenance Mode operations. The replica is not necessarily in synchrony with the master at the time that the replica start its updates.
When you are in Maintenance Mode, it is not safe to perform operations that rely on the replica and master being exactly in sync. The types of operations that you do in Maintenance Mode should be insensitive to whether the data in the replica is completely up-to-date. For example, adding a new column does not affect existing data values. However, if you change the values of existing columns while in Maintenance Mode, those changes might not match. Avoid perform DML operations while in Maintenance Mode.