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Migrating and upgrading
You can upgrade to the 14.10 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 Informix® Migration Guide describes how to move data manually between databases, servers, and computers.
Migration to and reversion from 14.10
Reverting from Informix® Version 14.10
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 Informix®
After preparing to revert, run the reversion utility and prepare to use the original database server.
Restore original configuration parameters
Replace the Informix® 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.

Migrating and upgrading
You can upgrade to the 14.10 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 Informix® Migration Guide describes how to move data manually between databases, servers, and computers.
  - Overview of migration
  - Migration to and reversion from 14.10
    - Preparing for migration to Version 14.10
      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.
    - Enterprise Replication and migration
      You must coordinate the migration of all servers that are involved in data replication.
    - 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 Informix® 14.10
      When you migrate to a new version of Informix®, you must complete required migration and post-migration tasks.
    - Reverting from Informix® Version 14.10
      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 , you must prepare your system for reversion to the pre-migration version of the database server.
      - Reverting from Informix®
        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® 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® 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.
        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 ON-Bar 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 DataBlade® modules
        You must register any DataBlade® 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

Restore original configuration parameters

Replace the Informix® 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.

You might also need to adjust the values of existing configuration parameters.