HP labors over repair for IMAGE
Databases LargeFile datasets cause
HP preached the message of investment
protection while it sold the HP 3000. The sermon apparently stuck at
the vendors labs. Engineers there have been toiling for months
on a repair that could make an IMAGE enhancement reliable at last
more than a year after HP stopped selling 3000s.
IMAGEs LargeFile Datasets (LFDS) have
been in repair mode for more than nine months, as HPs engineers
work to prevent data corruption which can occur while using LFDS. In
some cases an access to one of these datasets will corrupt the data
inside, an absolute no-no to the stickler customers who rely on
HP started the repairs after database utility
vendor Adager reported the problem. The company first detected the
problem during its internal tests of LFDS. Adagers customers
then began encountering data corruption when they used LFDS,
according to CEO Rene Woc. The problem has been so severe that Adager
has advised customers not to use LFDS and rely on Jumbo datasets
instead. Jumbo datasets are multi-file datasets that consist of
several chunks, each limited to a maximum of 4 GB.
HP provided LFDS with the best of intentions,
hoping to overcome a limitation of Jumbos: the Jumbo datasets did not
support dynamic dataset capacity expansion (called DDX for detail
datasets, MDX for masters). Starting with version C.10.01 of IMAGE,
HP 3000 TurboIMAGE databases with big datasets could use LargeFiles,
which rely on the relatively new MPE/iX ability to create files
larger than 4 GB. Adager offers a complimentary utility to convert a
database with Jumbo datasets to one which uses LFDS.
An LFDS is a single MPE/iX file that can be
as large as 128 GB. Such LargeFile datasets support dynamic dataset
capacity expansion, which makes capacity management less critical for
HP 3000 customers, according to Woc. But he said customers need to
take notice of the risks of using LFDS before HP finishes its fix.
The main thing is to be aware of the
issues, he said. Were in the bug avoiding business,
so we need to identify them, so we dont step on the land
A late February Internet message from Ken
Sletten, the last chairman of the SIG-IMAGE special interest group,
alerted customers that LFDS is seriously broke. Sletten
noted that HPs repair efforts were already overdue on a
deadline that had been extended several times. The patch is still in
process while HP has missed its own estimates of November and
December of 2004.
Not only did it not make the end of
2004, HP is now having to regroup at least to some extent on the
planned fix, Sletten said in his message. The patch
delivery date is now unknown.
The data corruption can occur for any
customer who uses LFDS, Sletten explained. Any TurboIMAGE entry
than spans the 4GB point of an LFDS will be corrupted by DBGET, and
will corrupt data during DBPUT, he said. These new datasets
always have one block that spans the 4GB point, unless the
dataset BlockLength results in an MPE record size of 128 half-words,
a rare event these days.
After getting notified by Adager of the
problem in April of 2004, HP has been working on the problem since
June. Now the HPs 3000 lifecycle is getting close to having
less than 18 months of technical resources left for IMAGE repairs.
Sletten and others are concerned that even if a patch for LFDS
surfaces in beta test, a 3000 community now leery of making changes
will avoid implementing it. A growing number of HP patches for the
3000 are struggling to get beta test results.
The problem is becoming more widespread when
customers use DBSCHEMA, according to Woc. The new DBSCHEMA default
creates datasets as LFDS; only issuing a $CONTROL JUMBO command in
DBSCHEMA avoids the broken LFDS format when the resulting datasets
are greater than 4 GB.
HP senior support engineer Cathlene Mc Rae
updated the HP 3000 community on the LFDS problem the day after
Sletten posted his message. If you were considering this LFDS
option, it is not working at this time, she said. The lab
is working on the problem and we hope to have something in the near
future. Customers who want to test the patch should open an HP
Response Center case, she added.
Some customers believe HP would do better to
remove LFDS altogether, since a significant pool of beta-testers for
the patch seems unlikely to surface. Meanwhile, the LFDS format has
been spreading. HPs designs dont allow Jumbo datasets to
coexist with LargeFile datasets in a single database. Customers who
have needed the DDX and MDX dynamic expansion capability on their
Jumbo datasets need to convert to LFDS, either with a DBUNLOAD/DBLOAD
or with the complimentary utility from Adager.
HPs repair efforts show that it is
protecting its investment in LFDS development. The vendor considered
an option to complete its design of Jumbo datasets several years ago,
a path that would have give Jumbos DDX and MDX capabilities.
In retrospect it seems it would have
been better to complete the original design idea on Jumbo
Datasets, said Sletten, and permanently forget about
using LFDS in TurboIMAGE. HP has indicated that extending the
capabilities of Jumbos is no longer an option.
MPE/iX versions 6.5, 7.0 and 7.5 all have
TurboIMAGE releases that permit LFDS. HPs Mc Rae said the
vendor is keeping Adager updated on the progress of the HP fix, and
offered to notify customers through the 3000-L mailing list when a
patch becomes available. The new code is being tested
now, Mc Rae reported at the end of February. A [release]
schedule has not yet been set.