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Streaming, a means of replicating User Defined Types in a replication environment.

IP.com Disclosure Number: IPCOM000011500D
Original Publication Date: 2003-Feb-26
Included in the Prior Art Database: 2003-Feb-26
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Abstract

Disclosed is a method for replicating User-Defined Types (UDT's) in an object-relational replication environment, addressing issues of data-opacity and differences in data representation between the source and target sites of the replication.

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  Streaming, a means of replicating User Defined Types in a replication environment.

   This invention allows the replication of User-Defined Types (UDT's) in an object-relational replication environment, addressing issues of data-opacity and differences in data representation between the source and target sites of the replication.

Several difficulties arise when attempting to replicate UDT's:

UDT's are opaque types whose data format and data representation are invisible

and unknown to the replication system. The data representation of the UDT at the source site may differ in format from the

data representation at the target site of the replication. For example, the source and target may be implemented on different machine architectures, or the source and target may be running different implementations of the UDT, with different data representations. In replicating a UDT instance to the target, one may want to do various data

conversions. For example, the source site may represent monetary amounts in US dollars, whereas the target may represent monetary amounts as Euros. The UDT may use and/or manage data kept outside the replication environment and

outside the object-relational system, for example, in a operating system file. In replicating an instance of such a UDT, such data must be replicated as well.

     In the remainder of this document we will use the term replicatable representation to refer to a representation of the data and values of a UDT instance that can be used by the replication system to replicate the values of a UDT instance from the source site, in such a manner that the target site can create, in the format of the target site, a UDT instance that is equivalent in data and values to the UDT instance at the source site. A replicatable representation addresses, at the least, the 4 issues listed above.

     This invention allows the replication system to convert a UDT instance at the source site that is in the format of the source site into an equivalent replicatable representation of the UDT instance, and to convert the replicatable representation of the UDT instance into an equivalent UDT instance in the format of the target site. This invention allows the replication system to obtain a replicatable representation of the UDT instance at the source site by invoking a method provided by the UDT to obtain the replicatable representation.

     This invention allows the replication system to convert the replicatable representation of the UDT instance to a UDT instance in the format of the target site by invoking a method provided by the UDT.

     One existing database management system implements UDT replication. It replicates to the target site the UDT instance data in the format at which it is kept at the source server. This method has the shortcoming that the representation of the UDT at the source and the representation of the UDT at the target must be identical, otherwise the replication will fail. It also does not allow data conversion...