ACC: How to Make a Database Replicable

MORE INFORMATION

To implement Microsoft Jet database engine replication, you need to convert a Microsoft Access database into a special, replicable format. There are three ways to make a database replicable:

• You can drag and drop the database file (.mdb) into the Briefcase on the Windows 95 or later or Windows NT 4.0 desktop.
• You can use the Create Replica command in Microsoft Access. (Point to Replication on the Tools menu and click Create Replica.)
• You can use the Replication Manager available with the Microsoft Office 97, Developer Edition or the Microsoft Access Developer's Toolkit for Windows 95 version 7.0.

When you convert a database into a replicable format, you are asked to make a backup copy of the database. You should click Yes to create the backup copy because once it is replicable, you cannot return the database to its non-replicated state.

The replication conversion process adds several components, modifies a few properties for existing objects, and adds new properties to a database. Specifically, replication makes the following changes to a database:

• A minimum of three new fields are added to each data table:
  1. The s_GUID field stores a globally unique identifier for each record.
  2. The s_Lineage field stores binary information about the history of changes to the record.
  3. The s_Generation field stores information about groups of changes. If a table has Memo or OLE data type fields, multiple s_Generation fields are added--one for each Memo or OLE field.
• Several System tables are added to the database to record the history of exchanges between replicas, the location of other replicas in the replica set, and other information required by the Microsoft Jet database engine.
• The NewValues property of AutoNumber fields will change from Increment to Random. This prevents any new records from receiving the same value as other new records in different replicas.
• The Properties collection in Data Access Objects (DAO) has five additional properties: DesignMasterID, KeepLocal, Replicable, ReplicaID, and ReplicationConflictFunction.
• The Replicable property for each object in the database is set to "T".