Because of the time needed for this check and the possible contention that the check can cause, schedule this check for times when activity is at its lowest. You should perform this check just before you create a level-0 backup.
Run the commands shown in Table 50 as part of the consistency check.
You can run each of these commands while the database server is in online mode. For information about how each command locks objects as it checks them and which users can perform validations, see oncheck in the IBM Informix Administrator's Reference.
In most cases, if one or more of these validation procedures detects an error, the solution is to restore the database from a dbspace backup. However, the source of the error might also be your hardware or operating system.
To validate system catalog tables, use the oncheck -cc command.
Each database contains its own system catalog, which contains information about the database tables, columns, indexes, views, constraints, stored procedures, and privileges.
If a warning appears when validation completes, its only purpose is to alert you that no records of a specific type were found. These warnings do not indicate any problem with your data, your system catalog, or even your database design. This warning indicates only that no synonym exists for any table; that is, the system catalog contains no records in the table syssyntable. For example, the following warning might appear if you validate system catalog tables for a database that has no synonyms defined for any table:
WARNING: No syssyntable records found.
However, if you receive an error message when you validate system catalog tables, the situation is quite different. Contact IBM Informix Technical Support immediately.
To validate data pages, use the oncheck -cD command.
If data-page validation detects errors, try to unload the data from the specified table, drop the table, re-create the table, and reload the data. For information about loading and unloading data, see the IBM Informix Migration Guide. If this procedure does not succeed, perform a data restore from a storage-space backup.
To validate extents in every database, use the oncheck -ce command.
Extents must not overlap. If this command detects errors, perform a data restore from a storage-space backup.
To validate indexes on each of the tables in the database, use the oncheck -cI command.
If this command detects errors, drop and re-create the affected index.
To validate logical logs and the reserved pages, use the oncheck -cR command.
To validate reserved pages, use the oncheck -cr command.
Reserved pages are pages that reside at the beginning of the initial chunk of the root dbspace. These pages contain the primary database server overhead information. If this command detects errors, perform a data restore from storage-space backup.
This command might provide warnings. In most cases, these warnings call your attention to situations of which you are already aware.
Execute oncheck -cs for each database to validate metadata for all smart large objects in a database. If necessary, restore the data from a dbspace backup.
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