Structure of a Mirror Chunk

Each mirror chunk must be the same size as its primary chunk. When a mirror chunk is created, the database server writes the contents of the primary chunk to the mirror chunk immediately.

The mirror chunk contains the same control structures as the primary chunk. Mirrors of blobspace, sbspace, or dbspace chunks contain the same physical contents as their primary counterpart after the database server brings them online.

Figure 1 illustrates the mirror-chunk structure as it appears after the chunk is created.
Figure 1. Mirror-Chunk Structure
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The mirror-chunk structure always shows no free space because all of its space is reserved for mirroring. For more information, see the chapter on what is mirroring in the IBM® Informix® Administrator's Guide.

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