Notes on Database Pattern Relationships

These Patterns build on each to solve increasingly more difficult problems. Note that this background color indicates notes and annotations that I wrote.

Excerpt from the Master-Master Replication Pattern

Table 1: Conflict Resolution Methods

Conflict	Method	Description
Update, delete	Priority based	Every database has a priority assigned to it. The replication unit from the database with the higher priority prevails.
Update	Value based	Rules defined on the values decide the winning replication unit. For example, if the data contains a timestamp, the more recent timestamp prevails.
Update	Merge	The values of both source and target are merged by operations such as: min, max, sum, average
Update, delete	Overwrite	The data in the target database is overwritten in every case. Unlike the priority-based method, this method does not require conflict detection.
All	Manual	After a conflict is detected, the replication is suspended until the conflict is resolved manually.
Uniqueness	Discard	If you try to insert data that exists in the target database, the new data is ignored.
Uniqueness	Append sequence	If you try to insert data that exists in the target database, the key value is changed to a new value. Such data must be merged manually later.

The Master-Master Replication Pattern builds upon these more basic Patterns.

·  Move Copy of Data. This pattern is the root pattern of this cluster; it presents the overall architecture to maintain redundant data by asynchronous writing of copies of data eventually after the data has been updated.

·  Data Replication. This pattern presents the architecture of a replication.

These notes are written from the point of that you are here.

·  Master-Master Replication. This pattern discusses a situation in which changes occur to a common set of data at either source or target, and the other party wants such changes replicated to it.

Other Patterns of Interest (These Patterns are basically the same but in a different scenario) or just skip ahead to Patterns that you can use next .

·  Master-Slave Cascading Replication. This pattern discusses a replication deployment where many targets want to subscribe to the replication set that is being replicated