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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
Migrating to Informix® 14.10
When you migrate to a new version of Informix®, you must complete required migration and post-migration tasks.
Completing required post-migration tasks
After you migrate, you must complete a series of post-migration tasks to prepare the new version of the server for use.
Verify the integrity of migrated data
Open each database with DB-Access and use oncheck to verify that data was not corrupted during the migration process.

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.
      - Migrating to the new version of Informix®
        After you prepare your databases for migration, you can migrate to the new version of Informix®.
      - Completing required post-migration tasks
        After you migrate, you must complete a series of post-migration tasks to prepare the new version of the server for use.
        For ON-Bar, copy the sm_versions file
        After migration, if you plan to use a storage manager other than the Informix® Primary Storage Manager, copy your previous sm_versions file to use with ON-Bar. Informix Primary Storage Manager does not use the sm_versions file.
        Finish preparing earlier versions of 12.10 databases for JSON compatibility
        To make databases that were created with earlier versions of Informix® 12.10 JSON compatible, you must complete some post-migration steps.
        Optionally update statistics on your tables after migrating
        Optionally run UPDATE STATISTICS on your tables and on UDRs that perform queries, if you have performance problems after migrating to the new version of Informix®.
        Review client applications and registry keys
        After you migrate a database server on the same operating system or move the database server to another compatible computer, review the client applications and sqlhosts file or registry-key connections. If necessary, recompile or modify client applications.
        Verify the integrity of migrated data
        Open each database with DB-Access and use oncheck to verify that data was not corrupted during the migration process.
        Back up Informix® after migrating to the new version
        Use a backup and restore tool (ON-Bar or ontape) to make a level-0 backup of the new database server. Do not overwrite the tapes that contain the final backup of the old database server.
        Tune the new version for performance and adjust queries
        After backing up the new server, you can tune the database server to maximize performance. If your queries are slower after the upgrade, there are steps you can take to adjust your configuration and queries.
        Register DataBlade® modules
        You must register any DataBlade® modules that you installed.
    - 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.
  - Migration of data between database servers
  - Data migration utilities

Verify the integrity of migrated data

Open each database with DB-Access and use oncheck to verify that data was not corrupted during the migration process.

You can also verify the integrity of the reserve pages, extents, system catalog tables, data, indexes, and smart large objects, as Commands for verifying the data integrity shows.

Table 1. Commands for verifying the data integrity
Action	oncheck Command
Check reserve pages	oncheck -cr
Check extents	oncheck -ce
Check system catalog tables	oncheck -cc `database_name`
Check data	oncheck -cD `database_name`
Check indexes	oncheck -cI `database_name`
Check smart large objects	oncheck -cs `sbspace_name`
Check smart large objects plus extents	oncheck -cS `sbspace_name`

If the oncheck utility finds any problems, the utility prompts you to respond to corrective action that it can perform. If you respond Yes to the suggested corrective action, run the oncheck command again to make sure the problem has been fixed.

The oncheck utility cannot fix data that has become corrupt. If the oncheck utility is unable to fix a corruption problem, you might need to contact Informix® Software Support before your proceed.

Important: If the value of the MAX_FILL_PAGES configuration parameter is 1, you must run oncheck -cD for all tables that include variable length data types (VARCHAR, NVARCHAR, and LVARCHAR), and take the suggested corrective action to avoid warnings about resetting the bitmap mode.