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Administering
In addition to administering the database server, you can tune performance, replicate data, and archive data.
Enterprise Replication
The HCL® Informix® Enterprise Replication Guide describes the concepts of data replication using Informix Enterprise Replication, including how to design your replication system, as well as administer and manage data replication throughout your enterprise.
About Enterprise Replication
Informix® Enterprise Replication generates and manages multiple copies of data at one or more sites, which allows an enterprise to share corporate data throughout its organization.
How Enterprise Replication Replicates Data
Data Capture
As the database server writes rows to the logical log, it marks rows that should be replicated. Later, Enterprise Replication reads the logical log to obtain the row images for tables that participate in replication.

Administering
In addition to administering the database server, you can tune performance, replicate data, and archive data.
- System administration
  These topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL Informix® database servers.
- Backup and Restore Guide
  The Informix® Backup and Restore Guide describes how to use the Informix ON-Bar and ontape utilities to back up and restore database server data. These utilities enable you to recover your databases after data is lost or becomes corrupted due to hardware or software failure or accident.
- Enterprise Replication
  The HCL® Informix® Enterprise Replication Guide describes the concepts of data replication using Informix Enterprise Replication, including how to design your replication system, as well as administer and manage data replication throughout your enterprise.
  - About Enterprise Replication
    Informix® Enterprise Replication generates and manages multiple copies of data at one or more sites, which allows an enterprise to share corporate data throughout its organization.
    - HCL Informix® Enterprise Replication technical overview
      Informix® Enterprise Replication is an asynchronous, log-based tool for replicating data between HCL Informix database servers. Enterprise Replication on the source server captures transactions to be replicated by reading the logical log, storing the transactions, and reliably transmitting each transaction as replication data to the target servers.
    - How Enterprise Replication Replicates Data
      - Data Capture
        As the database server writes rows to the logical log, it marks rows that should be replicated. Later, Enterprise Replication reads the logical log to obtain the row images for tables that participate in replication.
        Row Images
        Enterprise Replication evaluates the initial and final images of a row and any changes that occur between the two row images to determine which rows to replicate. Each row image contains the data in the row and the action that is performed on that row.
        Evaluate rows for updates
        Enterprise Replication evaluates rows for replication-key updates, for WHERE-clause column updates, and for multiple updates to the same row.
        Send queues and receive queues
        Enterprise Replication uses send and receive queues to receive and deliver replication data to and from database servers that participate in a replicate.
        Data Evaluation Examples
      - Data Transport
      - Applying replicated data
        Informix® Enterprise Replication uses a data-synchronization process to apply the replicated data to target database servers.
  - Planning and designing for Enterprise Replication
    Before you set up your replication system, plan how to include Enterprise Replication into your database server environment, design your database schema by following Enterprise Replication requirements, and then design your replication system between database servers.
  - Setting up and managing Enterprise Replication
    After you design your replication system, you define it and start replication.
  - Push data feature
  - Loopback replication
  - Appendixes

Data Capture

As the database server writes rows to the logical log, it marks rows that should be replicated. Later, Enterprise Replication reads the logical log to obtain the row images for tables that participate in replication.

Informix® database servers manage the logical log in a circular fashion; the most recent logical-log entries write over the oldest entries. Enterprise Replication must read the logical log quickly enough to prevent new logical-log entries from overwriting the logs Enterprise Replication has not yet processed.

If the database server comes close to overwriting a logical log that Enterprise Replication has not yet processed, by default, user transactions are blocked until Enterprise Replication advances. You can specify other responses to the potential for overwriting the Enterprise Replication replay position.

The row images that participate in replication are passed to Enterprise Replication for further evaluation.