|
|
|
SSChampion
Group: General Forum Members
Last Login: Today @ 2:21 AM
Points: 14,804,
Visits: 10,597
|
|
Comments posted to this topic are about the item Managing Transaction Logs
Gail Shaw
We walk in the dark places no others will enter
We stand on the bridge and none may pass
|
|
|
|
|
Forum Newbie
Group: General Forum Members
Last Login: Yesterday @ 2:54 PM
Points: 5,
Visits: 142
|
|
When do checkpoints happen? Are they automatic? Can they be invoked programmatically?
Besides simple recovery, are there other techniques to minimize the size of the transaction log?
Thank you,
Jake
|
|
|
|
|
Hall of Fame
Group: General Forum Members
Last Login: Thursday, November 12, 2009 7:14 AM
Points: 3,295,
Visits: 964
|
|
Excellent discussion... Useful one
|
|
|
|
|
SSCrazy
Group: General Forum Members
Last Login: 2 days ago @ 3:48 AM
Points: 2,032,
Visits: 1,598
|
|
Hi Gail
Nice article... presented in very easy to understand manner
One question may not be entirely related to this topic
Say there is a big data modification (update statement) going on and not all pages affected by the update stmt are in the buffer/memory. Will the pages not in the memory be first fetched into the memory and then changed ? Or will the change be in the log and then written to the disk without the pages being brought to the memory?
Thanks
"Keep Trying"
|
|
|
|
|
SSCarpal Tunnel
Group: General Forum Members
Last Login: Yesterday @ 4:47 AM
Points: 4,752,
Visits: 3,529
|
|
|
|
|
|
SSChampion
Group: General Forum Members
Last Login: Today @ 2:21 AM
Points: 14,804,
Visits: 10,597
|
|
Jake (10/30/2008)
When do checkpoints happen?
At regular intervals depending on the number and frequency of data modifications.
Are they automatic?
Yup.
Can they be invoked programmatically?
Yes. The command is CHECKPOINT. It's not something that's often needed/
Besides simple recovery, are there other techniques to minimize the size of the transaction log?
Keep transactions short. The tran log can only be truncated to the beginning of the oldest active transaction. If you have transactions that remain open for long periods of time, it will prevent log truncation.
Gail Shaw
We walk in the dark places no others will enter
We stand on the bridge and none may pass
|
|
|
|
|
SSChampion
Group: General Forum Members
Last Login: Today @ 2:21 AM
Points: 14,804,
Visits: 10,597
|
|
Chirag (10/31/2008)
Say there is a big data modification (update statement) going on and not all pages affected by the update stmt are in the buffer/memory. Will the pages not in the memory be first fetched into the memory and then changed ? Or will the change be in the log and then written to the disk without the pages being brought to the memory?
The query processor can only operate on pages in memory. If a query (read or change) requires a page that isn't in memory then the query processor requests that page and puts the query that needs it into a waiting state. The storage engine will go and fetch that page (issuing the appropriate IO requests to the OS), put it into memory and then signal the query processor that the page is there. The query that needed it will then be made runnable and can continue processing.
Bit of an over-simplification, but serves to explain.
Gail Shaw
We walk in the dark places no others will enter
We stand on the bridge and none may pass
|
|
|
|
|
SSChampion
Group: General Forum Members
Last Login: Today @ 2:21 AM
Points: 14,804,
Visits: 10,597
|
|
Anirban Paul (10/30/2008)
Excellent discussion... Useful one
ALZDBA (10/31/2008)
100% demystification 
Thank you. Glad you liked it.
Gail Shaw
We walk in the dark places no others will enter
We stand on the bridge and none may pass
|
|
|
|
|
SSCrazy
Group: General Forum Members
Last Login: 2 days ago @ 3:48 AM
Points: 2,032,
Visits: 1,598
|
|
GilaMonster (10/31/2008)
Chirag (10/31/2008)
Say there is a big data modification (update statement) going on and not all pages affected by the update stmt are in the buffer/memory. Will the pages not in the memory be first fetched into the memory and then changed ? Or will the change be in the log and then written to the disk without the pages being brought to the memory?
The query processor can only operate on pages in memory. If a query (read or change) requires a page that isn't in memory then the query processor requests that page and puts the query that needs it into a waiting state. The storage engine will go and fetch that page (issuing the appropriate IO requests to the OS), put it into memory and then signal the query processor that the page is there. The query that needed it will then be made runnable and can continue processing. Bit of an over-simplification, but serves to explain.
Thank you Gail. That explains things clearly. So would the same apply to BLOB data. Would BLOB data be brought into memory and then modified?
"Keep Trying"
|
|
|
|
|
SSChampion
Group: General Forum Members
Last Login: Today @ 2:21 AM
Points: 14,804,
Visits: 10,597
|
|
Chirag (10/31/2008)
Thank you Gail. That explains things clearly. So would the same apply to BLOB data. Would BLOB data be brought into memory and then modified?
Exactly the same. The query processor can only operate on pages in memory. The query processor has no knowledge of the disks and no ability to interact with the disks. That's what the storage engine does.
Gail Shaw
We walk in the dark places no others will enter
We stand on the bridge and none may pass
|
|
|
|
