Blobpages

A blobpage is the unit of disk-space allocation that the database server uses to store simple large objects (TEXT or BYTE data) within a blobspace.

You specify blobpage size as a multiple of the database server page size. Because the database server allocates blobpages as contiguous spaces, it is more efficient to store simple large objects in blobpages that are as close to the size of the data as possible. The following figure illustrates the concept of a blobpage, represented as a multiple (three) of a data page.
Figure 1. A blobpage on disk
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For information about how HCL Informix® structures data stored in a blobpage, see structure of a blobspace blobpage in the disk structures and storage topics of the HCL Informix Administrator's Reference.

Just as with pages in a chunk, a certain number of blobpages compose a chunk in a blobspace, as the following figure illustrates. A blobpage is always entirely contained in a chunk and cannot cross chunk boundaries.
Figure 2. A chunk in a blobspace, logically separated into a series of blobpages
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Instead of storing simple-large-object data in a blobspace, you can choose to store it in a dbspace. However, for a simple large object larger than two pages, performance improves when you store it in a blobspace. Simple large objects stored in a dbspace can share a page, but simple large objects stored in a blobspace do not share pages.

For information about how to determine the size of a blobpage, see Determine blobpage size. For a description of blobspaces, see Blobspaces.


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