Replication Concepts

The process of distributing a read-only copy of a study design, definition, and data to other locations in the environment is called replication.

This section describes the following replication concepts:

• Locations in a Distributed Study Environment Installation
  
• What Can You Replicate?
  
• What Methods of Replication Does Oracle Clinical Support?
  

Locations in a Distributed Study Environment Installation

Replication occurs among multiple database instances. Each database instance in your distributed installation must use the same release of Oracle Clinical.

Each included database instance is referred to as a location. The locations in an installation share Oracle Clinical data or dictionaries with other databases via Oracle Clinical replication capabilities. A location can refer to a separate database on the same computer or to a database in a different physical location.

This set of locations, which shares the same Global Library and can replicate study designs, definitions, and data, is referred to as an installation.

Within a distributed Oracle Clinical installation, you must identify the following locations:

• Global Library-Owning Location
  
• Study-Owning Location
  
• Lab-Owning Location
  

Global Library-Owning Location

The Global Library-owning location, which is also referred to as the global management location, owns and manages all the objects that compose data collection definitions for clinical studies.

These objects include:

• Global Library: questions, question groups, DVGs, standard affiliations, question categories, Global Library procedures, Global Library DCMs, and Global Library DCIs

• Codelists: installation reference codelists

• Global Lab: lab units and related information, lab panels, and textbook ranges

All other locations that are part of the distributed environment get read-only copies of information by replication. Keeping those copies up to date as things change in the Global Library-owning location requires planned follow-up replications.

Study-Owning Location

The study-owning location is the Oracle Clinical location where a particular study is designed and defined. Each study has only one owner. Different locations can be the study-owning locations for different studies.

The study-owning location:

• Creates and modifies the study design and definition.

• Controls the assignments of all patient positions to study-sharing locations.

• Provides a central repository of all collected study data.

  This repository includes data the study-owning location creates and data replicated from other study locations. Once data is centralized at the study-owning location, the data can then replicated to sharing locations.

If the study-owning location is not the Global Library-owning location, then the study-owning location must replicate the Global Library before beginning study definition. While creating and refining the study definition, the study-owning location can then perform Global Library replication at regular intervals to keep the Global Library up to date.

Lab-Owning Location

A lab-owning location maintains information about the attributes and ranges of its lab. Each lab has only one owner. Lab names must be globally unique across the installation. Any location that uses lab data from a lab it does not own must first replicate the lab information from the lab-owning location.

What Can You Replicate?

You can replicate the following Oracle Clinical objects:

• Global Library

• Study design

• Study definition

• Data

• Global Lab information

• Local labs and ranges

• Study randomization

What Methods of Replication Does Oracle Clinical Support?

In your distributed study environment, you can use one method or a combination of methods to replicate data across all the locations in your installation.

Oracle Clinical supports the following methods of replication:

• Standard Replication
  
• Disconnected Replication
  
• Symmetric Replication
  
• Comparison of Standard and Disconnected Replication
  

Standard Replication

Standard replication is a retrieving operation, that is, the location that requires the information must request it from the source location. In addition, standard replication uses a network connection to copy information from one location to another location.

Disconnected Replication

Disconnected replication supports bi-directional replication between locations without relying on a network connection. Instead, disconnected replication creates an export file that contains the data from the source location to be transferred to the target location. You choose how to transport the export file to the target location. For example, you can choose disk media, tape media, E-mail, or local area network (LAN). The target location then imports (or loads) the data from the export file.

Symmetric Replication

Symmetric replication copies only the supporting study design information and replication happens automatically. You do not need to select any menu option.

Comparison of Standard and Disconnected Replication

The final result of a standard replication is indistinguishable from a disconnected replication. The following table lists the key differences between the standard replication process and the disconnected replication process.

Table 12-1 Comparison of Standard versus Disconnected Replication

Standard Replication	Disconnected Replication
Requires a network connections to transfer information between locations.	Copies information between locations via file transfer. A network connection is not required.
The location requesting the data accesses the source database and copies the data. The owner of the data is not aware that the data is being copied.	The source location extracts the data to an export file and determines when to transfer the file to target locations. The owner of the data is actively involved in the process.
The study is marked as replicated only after the first replication successfully occurs.	The study is marked as replicated after the extract and export phase at the source location is complete, but before the import and load phase starts at the target locations. Therefore, existing restrictions about what can be done to a study once it has been replicated are imposed after the extract and export phase.
Supports full and incremental replication.	Supports full replication only.