Re: Checkpoint Vs Savepoints

tmalik_at_cs.jhu.edu wrote:

> Is there any difference between the terms checkpoint and savepoint?

Yes. They're spelled differently, for starters.

Savepoints usually apply to an individual transaction; it marks a point to which the transaction can be rolled back, so subsequent changes can be undone if necessary.

Checkpoints usually apply to whole database systems - the terminology gets confusing between manufacturers. Anyway, it marks a point at which the DBMS knows that what is on disk is consistent with what's in memory. Of course, fuzzy checkpoints make things more complex, but the idea remains valid. It gives a point in time at which recovery can start if the DBMS crashes - a point where the system knows where all the data is (which may be in a variety of places on disk other than just the obvious place - think of logical logs, physical logs, rollback segments and what have you).

-- 
Jonathan Leffler                   #include <disclaimer.h>
Email: jleffler_at_earthlink.net, jleffler_at_us.ibm.com
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