dlsc1032@dlscg1.UUCP (Alan Beal) (05/10/88)
I am interested in the various ways different DBMS systems handle recovery in
cases of hardware failure or media errors(ie. parity errors). My experiences
have been with UNISYS DMSII and UNIFY, and I have found the differences between
the methods of recovery utilized by both systems to be worlds apart. The
method of loading the entire database and reprocessing the auditted transactions
would be inappropriate for a database of any size or importance. While this
method is used by UNIFY, the Unisys database software allows for partial disk
pack recovery during concurrent update processing. Rollup, rollback, partial
database recovery, and full database rebuilds are easily handled by UNISYS
DMSII.
I would like to hear about the methods of recovery used by other database
management systems. In your discussions please keep in mind we would be talking
about database systems of considerable size, perhaps ranging from
1 to 100 gigabytes. Please do not restrict your discussion to only UNIX
DBMSs - I would like to hear about DBII, INGRES, DATACOMMDB, etc.
While it is nice to hear about theoritical database management systems, I am
only interested in present day, working, commercially available database
management systems.
Finally, I would like to express my contempt at those DBMS's that have never
developed better and faster methods of recovering database files. While
we have progressed in the methods of organizing and accessing data, we are
still in the Dark Ages as far as database recovery is concerned. Perhaps
this is a result of most vendors' belief that their hardware will never fail,
or our failure to require better recovery capabilities. Then again as my
experience has been, as long as the database is running when management comes
to work in the morning, it doesn't matter if one spends one hour recovering
the database or all night.
To quote an old instructor, "Never put your resume in a database, the only
time you will need it is when the database is down."
--
Alan Beal DLSC-ZBC Autovon 932-4160
Defense Logistics Services Center Commercial (616)961-4160
Battle Creek, MI 49015 FTS 552-4160
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