onmode -BC: Allow large chunk mode

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>>-onmode--+- -BC 1-+------------------------------------------><
           '- -BC 2-'   

Element Purpose Key Considerations
-BC 1 Enables support of large chunks, large offsets that are greater than 2 GB, and allows up to 32,768 chunks per instance. This option allows large chunks to be created. Reversion without dropping the dbspace is possible if no chunks are larger than 2 GB. Dbspaces and blobspaces without chunks greater than 2 GB remain in the old format. After a chunk larger than 2 GB is added to a dbspace or blobspace then all chunks added or altered in that dbspace or blobspace are in the new format.

See your IBM® Informix Administrator's Guide.

-BC 2 Allows large-chunk-only mode for all dbspaces. Reversion is not possible. Enables the 9.4 large chunk feature for all dbspaces and blobspaces, Any chunk or offset added or modified has the new format. Existing chunks that you do not alter remain in the old format.

See your IBM Informix Administrator's Guide

The onmode -BC (backward-compatible) commands are useful if you have converted from Informix® 9.40 (small chunk mode) to Informix 10.0 or later. When Informix 10.0 or later is first initialized (with the oninit -iyv command), by default it comes online with large chunk mode already fully enabled. Reversion is not possible. In the case of a newly initialized instance of Informix 10.0 or later, the onmode -BC commands will return an error.

Note: After executing the onmode -BC command, perform a complete system level-0 backup.

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