At 03:31 PM 4/28/99 -0400, Lafferty, Mike wrote:
>General question....We currently have a rather large DB (Jumbo datasets)
>for which we would like to assign B-tree indices....

As you are probably aware, IMAGE b-tree indexes are only attached to
master datasets.  Even if the master set happens to be a jumbo set,
it may be possible to attach a b-tree index, simply due to the volume
of data, size of key field, etc.  However, it is also possible to
have a standard master set whose volume/key size is too large for a
b-tree index.


>Being that TurboImage calculates and builds the KSAM files internally,
>in combination with the volume of our data and the MPE 4GB file limit,
>what will TurboImage "do" if these limits are exceeded ?.....

When you attempt to add the index in DBUTIL, if the volume of keys
exceeds the capacity of the KSAM file used for the b-tree, DBUTIL will
simply report an error.  Your database will be the same as is was before
the attempt was made.

>If they are exceeded, has anyone had any experiences with a workaround ?....

IMAGE does not have a workaround itself, as it only permits 1 KSAM file
per master set as the b-tree index file.  HP is currently working on
'LARGE FILES', which expand the maximum size of a single file from 4GB to
1TB.  In the initial release (late 1999/early 2000?) standard files and
NM KSAM files will be supported as large files.  This is to help support the
rapid growth of very large databases. (NOTE: I don't believe HP has plans
to support large files for CM KSAM.)

I would like to also point out that IMAGE itself will not take advantage
of large files for datasets initially.  One will still have to use IMAGE's
JUMBO dataset feature for datasets > 4GB.  However, because IMAGE utilizes
the KSAM interface to access the b-tree indexes, it will be possible to
have large KSAM b-trees.

<plug>

Today, Bradmark's indexing tool SUPRDEX can easily index large jumbo
datasets without being restricted to the 4GB file limit.  In addition,
SUPRDEX provides more types of indexing techniques than is available
with the current implementation of b-trees in IMAGE.

In addition, Bradmark's IMAGE database tool DBGENERAL contains a feature
which determines the maximum possible size of a dataset (option 1.4).  If
an IMAGE b-tree is attached to a dataset, the maximum size is adjusted
accordingly so as the information given does not exceed the capacity limit
of the corresponding KSAM file.  This same limit check will also be included
when changing master dataset capacities (3.3) or adding b-tree indexes
during database structural changes (5.6) in the next release.

</plug>




/jf
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