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The iWay Log Event Adapter for Informix works in conjunction with the following components:
iWay Service Manager is the heart of the Universal Adapter Framework and is an open transport service bus. Service Manager uses graphical tools to create sophisticated integration services without writing custom integration code by:
Its capability to manage complex adapter interactions makes it ideally suited to be the foundation of a service-oriented architecture.
The Informix CDC API allows external client applications to capture transactional data from an IBM Informix Dynamic Server database. This API also provides functions to capture transactional data. A variety of clients can run these functions, such as JDBC, ODBC, ESQL/C, and DB Access. The data is returned as CDC records by standard IBM Informix smart large object read functions.
The iWay Log Event Adapter for Informix uses the Informix CDC API to replicate data from an IBM Informix Dynamic Server database to another, heterogeneous, database (for example, Oracle). The following types of operations are captured:
The Informix CDC API starts capturing transactions for a particular table from the current logical log position and processes all transactions sequentially.
If data capture is stopped, it can be restarted at a specific point in the logical logs where data capture was stopped. The Informix CDC API cannot be used to go backwards in time through the logical logs to capture the history of a table or perform random seeking in the logical logs.
The Informix CDC API does not capture changes to table schemas or any other database changes. The API can only provide data as that data is changing, it does not provide an initial snapshot of the contents of a table.
Data types that are not supported by the Informix CDC API include TEXT, BYTE, row, structure, sequence, and user-defined data types.
The iWay Informix CDC Agent is a proprietary C-based application within the iWay Log Event Adapter for Informix, which leverages the Informix CDC API to access Logical Logs records data. The iWay Informix CDC Agent does not contain any hardcoded Informix account credentials.
Global variables for the program are retrieved from the Environment Configuration File. Database tables that are defined for replication are listed in the Table List Configuration File. Every entry in the table list has a table name and comma-separated columns list. The Table List Configuration File is generated by an ad-hoc shell script, using table name patterns as an input. All selected tables are listed along with all column names, excluding those of TEXT, BYTE, row, structure, sequence, and user-defined data types on which the Informix CDC API is not supported.
When the Informix database is updated (for example, by new transactions), the iWay Informix CDC Agent generates the Output CDC Data File in a specified directory, which identifies the transactions that occurred in the database. For each transaction, the output file is updated with XML data, a transaction ID, and the type of transaction.
The iWay Log Event Listener is a component of an iWay Service Manager (iSM) channel that is configured for a CDC Subscription. It listens for Output CDC Data Files in the Subscription output directory. The Output CDC Data Files contain transaction records in XML format. As soon as a new record is appended to a file in the Subscription output directory, the listener sends it to the iWay CDC SQL Batch Agent.
The iWay Log Event Listener interprets a carriage return character as a record delimiter. The listener keeps track of the last record that is read. If the listener is restarted, it resumes listening from that last record in the file.
The iWay CDC SQL Batch Agent (com.ibi.agents.XDCDCSQLBatchAgent) is a component of an iWay Service Manager (iSM) channel that is configured for a CDC Subscription. This agent is used to convert XML transaction records into ANSI SQL statements (INSERT, UPDATE, DELETE) and apply them to the target database tables. Output from the iWay Log Event Listener is used as input for the iWay CDC SQL Batch Agent. The agent must be configured to access a target database system (for example, Oracle).
SQL statements are grouped by transaction batches in the temporary files. A temporary batch file is created for every BEGIN_TX record and the SQL statements are appended to the file. When a COMMIT_TX statement is met, the SQL batch is applied to the target database. If a ROLBK_TX statement occurs, all transaction statements in the batch file are discarded.
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