Replication Server translates commands from the primary database into Replication Server functions that represent data server operations such as insert, delete, select, begin transaction, and so on. It distributes these functions to remote Replication Servers in the system, where they execute those operations in remote databases.
The primary Replication Server distributes functions in the same format regardless of the type of data server that actually updates the replicated data. Functions are not database-specific. They include all the data needed to perform the operation, but they do not specify the syntax needed to complete the operation at the destination data server.
The remote Replication Server converts functions to commands specific to the destination data servers where they are executed. A function string contains the database-specific instructions for executing a function. The replicate Replication Server managing a database uses an appropriate function string to map the function to a set of instructions for the data server. For example, the function string for the rs_insert function provides the actual language to be applied in a replicate database.
This separation between functions and data server commands lets you maintain replicated data among heterogeneous data servers. Replication Server allows you to customize function strings, specifying how Replication Server functions map to SQL commands. You can create function strings if you require customized data server operations. You customize replicated data applications by changing the way operations are performed at the destination database.
Function strings are grouped into function-string classes, so you can group mappings of functions to commands according to data server. Replication Server provides function-string classes for Adaptive Server Enterprise, Oracle, Microsoft SQL Server, IBM DB2 UDB, and other databases. You can create new derived function-string classes in which you customize certain function strings and inherit all others from these or other classes. You can also create entirely new classes in which you create all new function strings.
You may also need to create function strings for replicated functions, which allow you to execute stored procedures on remote databases. You must create a function string for any replicated function for which Replication Server does not automatically generate a function string in the function-string class used by the destination database.