They are used to share data on a network. DBMS standards for distributed databases:
SQL - Structured Query Language is a database access language. It is used by most client/server database applications.
ODBC - Open Database Connectivity (ODBC) from Microsoft lets application developers integrate database connections in applications. It is an application programming interface (API). ODBC drivers convert an application's query into SQL and send it to the database engine program.
DRDA - Distributed Relational Database Architecture is from IBM.
When information is processed in a distributed database, it is called a transaction. The two phases of a transaction are:
Write or Update - The data is temporarily updated. An abort can cancel what this phase did by removing the changed data from a temporary storage area.
Commit - The changed data is made permanent in the database.
Databases store multiple copies of the data which is called replication. They must be sure the various copies of the database on various servers is accurate with identical data. Data is also partitioned into smaller blocks of data.
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