Oracle Data Integrator 11g Product Overview and Architecture

The purpose of ETL (Extract, Load, Transform) tools is to help with the consolidation of data that is dispersed throughout the information system. Data is stored in disparate applications, databases, files, operating systems, and in incompatible formats. The consequences of such a dispersal of the information can be dire, for example, different business units operating on different data will show conflicting results and information cannot be shared across different entities of the same business. Imagine the marketing department reporting on the success of their latest campaign while the finance department complains about its lack of efficiency. Both have numbers to back up their assertions, but the numbers do not match! What could be worse than a shipping department that struggles to understand customer orders, or a support department that cannot confirm whether a customer is current with his/her payment and should indeed receive support? The examples are endless. The only way to have a centralized view of the information is to consolidate the data—whether it is in a data warehouse, a series of data marts, or by normalizing the data across applications with master data management (MDM) solutions. ETL tools usually come into play when a large volume of data has to be exchanged (as opposed to Service-Oriented Architecture infrastructures for instance, which would be more transaction based). In the early days of ETL, databases had very weak transformation functions. Apart from using an insert or a select statement, SQL was a relatively limited language. To perform heavy duty, complex transformations, vendors put together transformation platforms—the ETL tools. Product Overview Over time, the SQL language has evolved to include more and more transformation capabilities. You can now go as far as handling hierarchies, manipulating XML formats, using analytical functions, and so on. It is not by chance that 50 percent of the ETL implementations in existence today are done in plain SQL scripts—SQL makes it possible. This is where the ODI ELT architecture (Extract-Load-Transform—the inversion in the acronym is not a mistake) comes into play. The concept with ELT is that instead of extracting the data from a source, transforming it with a dedicated platform, and then loading into the target database, you will extract from the source, load into the target, then transform into the target database, leveraging SQL for the transformations. To some extent, ETL and ELT are marketing acronyms. When you look at ODI for instance, it can perform transformations on the source side as well as on the target side. You can also dedicate some database or schema for the staging and transformation of your data, and can have something more similar to an ETL architecture. Similarly, some ETL tools all have the ability to generate SQL code and to push some transformations at the database level. The key differences then for a true ELT architecture are as follows: • The ability to dynamically manage a staging area (location, content, automatic management of table alterations) • The ability to generate code on source and target systems alike, in the same transformation • The ability to generate native SQL for any database on the market—most ETL tools will generate code for their own engines, and then translate that code for the databases—hence limiting their generation capacities to their ability to convert proprietary concepts • The ability to generate DML and DDL, and to orchestrate sequences of operations on the heterogeneous systems In a way, the purpose of an ELT tool is to provide the comfort of a graphical interface with all the functionality of traditional ETL tools, to keep the efficiency of SQL coding with set-based processing of data in the database, and limiting the overhead of moving data from place to place. In this chapter we will focus on the architecture of Oracle Data Integrator 11g, as well as the key concepts of the product. The topics we will cover are as follows: • The elements of the architecture, namely, the repository, the Studio, the Agents, the Console, and integration into Oracle Enterprise Manager • An introduction to key concepts, namely, Execution Contexts, Knowledge Modules, Models, Interfaces, Packages, Scenarios, and Load Plans ODI product architecture Since ODI is an ELT tool, it requires no other platform than the source and target systems. But there still are ODI components to be deployed: we will see in this section what these components are and where they should be installed. The components of the ODI architecture are as follows: • Repository: This is where all the information handled by ODI is stored, namely, connectivity details, metadata, transformation rules and scenarios, generated code, execution logs, and statistics. • Studio: The Studio is the graphical interface of ODI. It is used by administrators, developers, and operators. Product Overview • Agents: The Agents can be seen as orchestrators for the data movement and transformations. They are very lightweight java components that do not require their own server—we will see in detail where they can be installed. • Console: The Console is a web tool that lets users browse the ODI repository, but it is not a tool used to develop new transformations. It can be used by operators though to review code execution, and start or restart processes as needed. • The Oracle Enterprise Manager plugin for ODI integrates the monitoring of ODI components directly into OEM so that administrators can consolidate the monitoring of all their Oracle products in one single graphical interface. At a high level, here is how the different components of the architecture interact with one another. The administrators, developers, and operators typically work with the ODI Studio on their machine (operators also have the ability to use the Console for a more lightweight environment). All Studios typically connect to a shared repository where all the metadata is stored. At run time, the ODI Agent receives execution orders (from the Studio, or any external scheduler, or via a Web Service call). At this point it connects to the repository, retrieves the code to execute, adds last minute parameters where needed (elements like connection strings, schema names where the data resides, and so on), and sends the code to the databases for execution. Once the databases have executed the code, the agent updates the repository with the status of the execution (successful or not, along with any related error message) and the relevant statistics (number of rows, time to process, and so on). ODI repository To store all its information, ODI requires a repository. The repository is by default a pair of schemas (called Master and Work repositories) stored in a database. Unless ODI is running in a near real time fashion, continuously generating SQL code for the databases to execute the code, there is no need to dedicate a database for the ODI repository. Most customers leverage existing database installations, even if they create a dedicated tablespace for ODI. Repository overview The only element you will never find in the repository is the actual data processed by ODI. The data will be in the source and target systems, and will be moved directly from source to target. This is a key element of the ELT architecture. All other elements that are handled through ODI are stored into the repository. An easy way to remember this is that everything that is visible in the ODI Studio is stored in the repository (except, of course, for the actual data), and everything that is saved in the ODI Studio is actually saved into the repository (again, except for the actual data). The repository is made of two entities which can be separated into two separate database schemas, namely, the Master repository and the Work repository. We will look at each one of these in more detail later, but for now you can consider that the Master repository will host sensitive data whereas the Work repository will host project-related data. A limited version of the Work repository can be used in production environments, where the source code is not needed for execution. Repository location Before going into the details of the Master and Work repositories, let's first look into where to install the repository. The repository is usually installed in an existing database, often in a separate tablespace. Even though ODI is an Oracle product, the repository does not have to be stored in an Oracle database (but who would not use the best database in the world?). Generally speaking, the databases supported for the ODI repository are Oracle, Microsoft SQL Server, IBM/DB2 (LUW and iSeries), Hypersonic SQL, and Sybase ASE. Specific versions and platforms for each database are published by Oracle and are available at: http://www.oracle.com/technetwork/middleware/ias/downloads/fusioncertification- 100350.html. It is usual to see the repository share the same system as the target database. We will now look into the specifics of Master and Work repositories. Master repository As stated earlier, the Master repository is where the sensitive data will be stored. This information is of the following types: • All the information that pertains to ODI users privileges will be saved here. This information is controlled by administrators through the Security Navigator of the ODI Studio. We will learn more about this navigator when we look into the details of the Studio. • All the information that pertains to connectivity to the different systems (sources and targets), and in particular the requisite usernames and passwords, will be stored here. This information will be managed by administrators through the Topology Navigator. • In addition, whenever a developer creates several versions of the same object, the subsequent versions of the objects are stored in the Master repository. Versioning is typically accessed from the Designer Navigator. Work repository Work repositories will store all the data that is required for the developers to design their data transformations. All the information stored in the Work repository is managed through the Designer Navigator and the Operator Navigator. The Work repository contains the following components: • The Metadata that represents the source and target tables, files, applications, message buses. These will be organized in Models in the Designer Navigator. • The transformation rules and data movement rules. These will be organized in Interfaces in the Designer Navigator. • The workflows designed to orchestrate the transformations and data movement. These are organized in Packages and Load Plans in the Designer Navigator. • The jobs schedules, if the ODI Agent is used as the scheduler for the integration tasks. These can be defined either in the Designer Navigator or in the Operator Navigator. • The logs generated by ODI, where the generated code can be reviewed, along with execution statistics and statuses of the different executions (running, done successfully or in error, queued, and so on). The logs are accessed from the Operator Navigator. Execution repository In a production environment, most customers do not need to expose the source code for the processes that are running. Modifications to the processes that run in production will have to go through a testing cycle anyway, so why store the source code where one would never access it? For that purpose, ODI proposes an execution repository that only stores the operational metadata, namely, generated code, execution results, and statistics. The type of Work repository (execution or development) is selected at installation time. A Work repository cannot be converted from development to execution or execution to development—a new installation will be required if a conversion is needed. Studio The ODI Studio is the graphical interface provided to all users to interact with ODI. People who need to use the Studio usually install the software on their own machine and connect to a shared repository. The only exception would be when the repository is not on the same LAN as the Studio. In that case, most customers use Remote Terminal Service technologies to ensure that the Studio is local to the repository (same LAN). Only the actual display is then sent over the WAN. Agent The ODI Agent is the component that will orchestrate all the operations. If SQL code must be executed by a database (source or target), the agent will connect to that database and will send the code (DDL and DML, as needed) for that database to perform the transformations. If utilities must be used as part of the transformations (or, more likely, as part of the data transfer) then the agent will generate whatever configuration files or parameter files are required for the utility, and will invoke this utility with the appropriate parameters—SQL Loader, BCP, Multiload, and NZload are just a small list of such utilities. There are two types of ODI Agent, namely, the standalone agent (available in all releases of ODI) and the JEE agent (available with ODI 11g and after) that runs on top of WebLogic Server. Each type has its own benefits, and both types of agents can co-exist in the same environment: • The JEE agent will take advantage of Weblogic in terms of high availability and pooling of the connections The standalone agents are very lightweight and can easily be installed on any platform. They are small Java applications that do not require a server. A common configuration is to use the JEE agent as a "Master" agent, whose sole purpose it is to distribute execution requests across several child agents. These children can very well be standalone agents. The master agent will know at all times which children are up or down. The master agent will also balance the load across all child agents.