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rollforward

  what is rollforwrd data in oracle after instance crash and what happens during rollforward?
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laksirib76
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laksirib76
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sachinkaggrawalCommented:
when we starts any transaction in the oracle, normally we make some changes in the database tables.
Now when we commit  these changes, all the changes from dbcache are written to disk datafiles. And some SCN is generated which is stamped in the redolog files. now suppose that after commit the data from redo buffer is written to redo file. after this the commited statement will be shown to the user.

but if now before this data being written to datafiles, the instance crashed. now this commited data which is not written to datafiles is rollforward data.

when the oracle instance starts again then this data is written to datafiles during instance recovery. this process of writing data to disk, in which the oracle comes to an consistent state, which was before crash, is known as rollforwarding state.
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