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How do I enable large chunk sizes in Informix 9.4 ?

In order to use the large (> 2gb) chunk size feature in Informix 9.4:


The size of chunks for dbspaces is 4 terabytes for a 2-kilobyte page. Chunks can reside anywhere in a 64-bit address space. To activate the creation of large chunks. you must use the onmode utility. The onmode utility uses a -BC flag to control the availability of large chunks, chunks greater than 2 gigabytes.

When the database server is first migrated to version 9.4, large chunks are not allowed. You must first run onmode -BC 1 to allow large chunks to be created.

However, the server continues to write small chunks to dbspaces and blobpages in version 9.3 and earlier previous formats. The server writes to that dbspace or blobspace in the 9.4 version format only when a large chunk is added to a dbspace or blobspace.

To complete the conversion to version 9.4 format, you must run onmode -BC 2. This will cause all server writes to be in the 9.4 version format.

If, during server initialization, the root chunk is a large chunk, the onmode -BC 1 step is skipped and -BC 2 mode is automatically initialized.