changes "during checkpointing"
In regards to 9.1.x, I would like to learn some details of the nature of "checkpointing"
=== Question 1 ===
- page 123 is dirty
- "checkpointing" starts
- page 123 gets written to disk, as part of this checkpoint
- page 123 gets modified again
? Does it get written to disk again, as part of this checkpoint?
- "checkpointing" finishes
=== Question 2 ===
- page 123 is dirty
- "checkpointing" starts
- page 123 gets modified again
- page 123 gets written to disk, as part of this checkpoint
? So does the most recent mod get written to disk, even if that mod is not committed yet ?
- "checkpointing" finishes
=== Question 3 ===
When does the full-page-writing to WAL happen ?
Is it after the start of the "checkpointing" or after the finish of the "checkpointing" ?
Thanks,
-dvs-
On Fri, Jan 11, 2013 at 1:04 PM, Sahagian, David <david.sahagian@emc.com> wrote:
In regards to 9.1.x, I would like to learn some details of the nature of
“checkpointing”=== Question 1 ===
- page 123 is dirty
- "checkpointing" starts
- page 123 gets written to disk, as part of this checkpoint
- page 123 gets modified again
? Does it get written to disk again, as part of this checkpoint?
No, the checkpointer doesn't write it again.
=== Question 2 ===
- page 123 is dirty
- "checkpointing" starts
- page 123 gets modified again
- page 123 gets written to disk, as part of this checkpoint
? So does the most recent mod get written to disk, even if that mod is not
committed yet ?
Yes, it the most recent version that gets written. The notion of
"committed' does not really apply to pages.
=== Question 3 ===
When does the full-page-writing to WAL happen ?
Is it after the start of the "checkpointing" or after the finish of the
"checkpointing" ?
The start.
Cheers,
Jeff
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