Welcome
Migrating and upgrading
You can upgrade to the 15.0.0 release of HCL Informix® or migrate from other database servers to Informix. Upgrading is an in-place migration method that uses your existing hardware and operating system software. Some changes to the Informix database server can affect upgrading from a previous release.
Migrating Informix® database systems
The HCL Informix® Migration Guide describes how to move data manually between databases, servers, and computers.
Migration to and reversion from 15.0.0
Reverting from Version 15.0.0
As long as your Version 15.0.0 instance is running in compatibility mode, you can revert to the version of the database server from which you migrated. When you run the reversion utility, you specify the target server for reversion and then Informix® checks your database. If necessary, Informix might tell you to drop new objects, before automatically converting your data into the target server.
Reverting from Version 15.0.0
After preparing to revert, run the reversion utility and prepare to use the original database server.
Back up the database server after reversion
After you complete the reversion, use or ontape to make a level-0 backup of the database server to which you reverted.

HCL Informix® V15.0.0 documentation
Welcome to the documentation for HCL Informix® 15.0.0 and related client tools and products.
Product overview
HCL Informix® is a fast and scalable database server that manages traditional relational, object-relational, and dimensional databases. Its small footprint and self-managing capabilities are suited to embedded data-management solutions.
Installing
These topics describe how to install HCL Informix® database servers, client products, and modules.
Administering
In addition to administering the database server, you can tune performance, replicate data, and archive data.
Migrating and upgrading
You can upgrade to the 15.0.0 release of HCL Informix® or migrate from other database servers to Informix. Upgrading is an in-place migration method that uses your existing hardware and operating system software. Some changes to the Informix database server can affect upgrading from a previous release.
- Migrating Informix® database systems
  The HCL Informix® Migration Guide describes how to move data manually between databases, servers, and computers.
  - Overview of migration
  - Migration to and reversion from 15.0.0
    - Preparing for migration to Version 15.0.0
      Before you install the new version of Informix®, you must prepare the database server environment for migration by performing specified pre-migration tasks. If you are also migrating from 32-bit to 64-Bit database servers, you must perform additional tasks.
    - and Upgrading
      The server nodes in your Enterprise Replication (ER) domain can run different versions and fixpack levels. On the other hand, new features might only be available between servers running the new version, and administrative ‘cdr’ commands should be run from the newest version environment.
    - High-availability cluster migration
      You must coordinate the migration and reversion of all servers that are involved in high-availability clusters. You can use a rolling upgrade in some cases to update servers while the cluster is online, with minimal interruption to client applications. Otherwise, you must schedule cluster downtime to upgrade the servers. A cluster must be offline to reverse an upgrade or revert to an earlier release.
    - Migrating to 15.0.0
      When you migrate to a new version of Informix®, you must complete required migration and post-migration tasks.
    - Reverting from Version 15.0.0
      As long as your Version 15.0.0 instance is running in compatibility mode, you can revert to the version of the database server from which you migrated. When you run the reversion utility, you specify the target server for reversion and then Informix® checks your database. If necessary, Informix might tell you to drop new objects, before automatically converting your data into the target server.
      - Preparing to revert
        If you used Version 15.0.0, you must prepare your system for reversion to the pre-migration version of the database server.
      - Reverting from Version 15.0.0
        After preparing to revert, run the reversion utility and prepare to use the original database server.
        Run the reversion utility
        After preparing to revert, run the reversion utility by using an onmode -b command.
        Restore original configuration parameters
        Replace the Informix® Version 15.0.0 ONCONFIG configuration file with the ONCONFIG file that you saved before you migrated. Alternatively, you can remove configuration parameters that the earlier database server does not support.
        Restore original environment variables
        Reset the environment variables to values that are appropriate for the earlier database server.
        Remove Any Communications Support Module Settings
        If your Informix® Version 15.0.0 instance used CSMs, edit the sqlhosts file to remove any csm option settings that are not supported in the older database server.
        Recompile Java™ user-defined routines
        After you revert and before you start the earlier server, recompile Java™ user-defined routines (UDRs) that were compiled with a Java development kit version that is earlier than or equal to the version included with the previous server.
        Reinstall and start the earlier database server
        Reinstall and configure the earlier version of the database server.
        Add JSON compatibility to databases that were created in 12.10.xC1
        Databases that were created in Informix® 12.10.xC1 are not JSON compatible. In 12.10.xC2 or 12.10.xC3 you can run a script to make those databases JSON compatible. You do not have to run the script after you upgrade to 12.10.xC4 or later fixpacks because all databases are made JSON compatible during conversion.
        Optionally update statistics on your tables after reverting
        Optionally run UPDATE STATISTICS on your tables and on UDRs that perform queries, if you have performance problems after reverting to the previous version of the database server or to a database server on a different operating system.
        Update statistics on some system catalog tables after reverting
        Verify the integrity of the reverted data
        Before you allow users to access the databases, check the integrity of the reverted data.
        Back up the database server after reversion
        After you complete the reversion, use or ontape to make a level-0 backup of the database server to which you reverted.
        Return the database server to online mode
        To bring the old database server online, run the onmode -m command.
        Register modules
        You must register any modules that your databases require. Built-in database extensions automatically revert to the version included in the database server to which you reverted.
  - Migration of data between database servers
  - Data migration utilities
Client APIs and tools
You can use the HCL Informix® implementation of client APIs to develop applications for Informix database servers.
Embedding Informix®
When you embed HCL Informix®, you can use enterprise-class high-availability and high performance with embeddability features such as easy programmability, a small disk and memory footprint, and silent deployment.
Extending Informix®
Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix includes many built-in extensions that are fully integrated in the database server. Informix also provides modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix.
Data warehousing
In addition to designing and implementing Informix® dimensional databases, you can use tools to create data warehouse applications and optimize your data warehouse queries.
Designing databases
The first step in creating a relational database is to construct a data model, which is a precise, complete definition of the data you want to store. After you prepare your data model, you must implement it as a database and tables. To implement your data model, you first select a data type for each column and then you create a database and tables and populate the tables with data. You can also implement fragmentation strategies and control access to your data.
JSON compatibility
You can use the popular JSON-oriented query language created by MongoDB to interact with data stored in HCL Informix®.
Security
You can secure your Informix® database server and the data that is stored in your Informix databases. You can encrypt data, secure connections, control user privileges and access, and audit data security.
SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
Troubleshooting HCL Informix®
Several troubleshooting techniques, tools, and resources are available for resolving problems that you encounter in your HCL Informix® database server environment.

Back up the database server after reversion

After you complete the reversion, use or ontape to make a level-0 backup of the database server to which you reverted.

For more information about making backups, see your HCL® Informix® Backup and Restore Guide.

Important: Do not overwrite the tapes that you used to back up your source database server.