onstat -d/-D DBSpaces and Chunks

M Mirrored
N Not mirrored
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D Down
L Being logically recovered
P Physically recovered, waiting for logical recovery
R Being recovered
U Not Backed up
X Newly mirrored
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B	Blobspace
S	Sbspace
T	Temporary dbspace
U	Temporary sbspace
W	Temporary dbspace on primary server 
	[only shown on SDS servers]
Position 4: 
<div class="onstat-div"><pre class="legacy">
B	DBSpace with chunks larger than 2GB
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A	The dbspace is auto-expandable, i.e. 
    SP_AUTOEXPAND is enabled 
    AND 
    (
    the dbspace is configured with a create size 
    OR 
    extend size that is not zero.
    )
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Position 6:
<div class="onstat-div"><pre class="legacy">
E	The storage space is encrypted.
</div>

P Primary chunk
M Mirror chunk
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O OnLine
D Down
I Inconsistent
N Renamed and either Down or Inconsistent
R Recovery
X Newly Mirrored
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- Data DBSpace
B BLOB DBSpace
S Smart BLOBSpace
</div>

B	DBSpace with chunks larger than 2GB
</div>

E	Identifies the chunk as extendable
</div>

For cooked file chunks

C	On AIX the concurrent I/O option is enabled
D	The direct I/O option is enabled 

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Fragment elimination and parallelism is performed at the DBSpace level.

DBSpace numbers and chunk numbers are automatically assigned and are reused if one happens to be dropped.

When looking for down chunks, it is easiest to 'grep' for the letters 'PD' rather than try to pick 'PD' out of a list of 'PO's, since the two values tend to look very similar.

There are two types of chunks, primary and mirrored.

Primary does not refer to the first chunk for a DBSpace; rather, it is a way to refer a chunk that is not the actual mirror.

Pathnames for chunks should be links to the device file. This will provide for greater flexibility, should a disaster recovery situation occur.

The initial 53 pages of the first chunk for a DBSpace are used for 2 reserved pages, 1 chunk free list page and 50 pages for the TBLSpace partition.

The second and follow-on chunks for a DBSpace will initially have an overhead of 3 pages: 2 reserved pages and 1 chunk free list page.

Different versions of Informix Dynamic Server are designed to handle different maximum numbers of chunks; the current maximum is 32K If a chunk contains the MetaData for a Smart BLOBSpace, the offset listed will indicate: Metadata The onstat -D only displays the page-read and page-write information for the first 50 chunks in each space.

onstat -d update will generate the blobpage free list

If mirroring is being performed, the primary and mirror chunks should be on different controllers.

It is important to ensure that your temporary DBSpaces are actually labelled as temporary. You should see a 'T' in the second position of the second flags column of the DBSpace section.