|
-
I just read that RMAN can take Incremental-Cumulative backups at three levels 0, 1 and 2.
I am confused as to why * ONLY * three levels? Lets say I have the Level 2 backup; if some blocks get modified after this, will the backup again be called as Level 3 or still Level 2??
Awaiting for some help.
-
Incremental backup only copies those Oracle blocks modified since a previous incremental backup (level <= n)
Cumulative backup copies all Oracle blocks changed since the previous backup at a level less than n (level < n)
and there arent 3 levels only, you can define up to 5 (0 to 4)
considering we are using incremental-cumulative backup:
if I have a level 0 backup on Sunday, a level 1 backup on Tuesday, and on Wednesday I have a level 2 backup then on Wednesday I will copy changed blocks since Tuesday, if on Thursday I have a level 1 backup I will be copying changed blocks since level 0 since level 0 < level 1, look like this
Sunday level 0
Tuesday level 1
Wednesday level 2
Thursday level 1
We are on Thursday, previous backup level is 2, is Thursday level 1 less than 2? No so go another day back, is Tuesday backup level less than 1? No so go back again, is level 0 less than 1? YES! So we backup all changed blocks since level 0
if we were using incremental backup it will be like this
Sunday level 0
Tuesday level 1
Wednesday level 2
Thursday level 1
On Wednesday I will be copying changed blocks since Tuesday since level 1 <= level 2
On Thursday I will be copying changed blocks since Tuesday since level 1 <= level 1
All these incremental backup business is not complicated just think:
my current backup level has to be BIGGER OR EQUAL to last backup level if I want to perform incremental backup
current backup level >= last backup level =====> incremental
my current backup level has to be BIGGER to last backup level if I want to perform incremental backup
current backup level > last backup level =====> cumulative
[Edited by pando on 10-01-2002 at 06:42 AM]
-
Originally posted by pando
Incremental backup only copies those Oracle blocks modified since a previous incremental backup (level <= n)
Cumulative backup copies all Oracle blocks changed since the previous backup at a level less than n (level < n)
and there arent 3 levels only, you can define up to 5 (0 to 4)
considering we are using incremental-cumulative backup:
if I have a level 0 backup on Sunday, a level 1 backup on Tuesday, and on Wednesday I have a level 2 backup then on Wednesday I will copy changed blocks since Tuesday, if on Thursday I have a level 1 backup I will be copying changed blocks since level 0 since level 0 < level 1, look like this
Sunday level 0
Tuesday level 1
Wednesday level 2
Thursday level 1
We are on Thursday, previous backup level is 2, is Thursday level 1 less than 2? No so go another day back, is Tuesday backup level less than 1? No so go back again, is level 0 less than 1? YES! So we backup all changed blocks since level 0
if we were using incremental backup it will be like this
Sunday level 0
Tuesday level 1
Wednesday level 2
Thursday level 1
On Wednesday I will be copying changed blocks since Tuesday since level 1 <= level 2
On Thursday I will be copying changed blocks since Tuesday since level 1 <= level 1
All these incremental backup business is not complicated just think:
my current backup level has to be BIGGER OR EQUAL to last backup level if I want to perform incremental backup
current backup level >= last backup level =====> incremental
my current backup level has to be BIGGER to last backup level if I want to perform incremental backup
current backup level > last backup level =====> cumulative
[Edited by pando on 10-01-2002 at 06:42 AM]
Many thanks for spending so much time. I am still confused with all these:
1)On Thursday, how did it become Level "1"?? Say blocks of Level 2 of Wednesday changed. That means these changed blocks of Level "2" has to be backed up in which case it becomes Level "3", ain't it? I am missing something here.
2)In SYBEX series of books, he expalains that Incremental is of two types: Diffrential and Cumulative. He also says that there are Levels 0, 1 and 2 only. Is this a mistake in the book.
Awaiting your kind response.
-
I just made up for that Thursday level 1 backup, I can make it level 0, 2, or 3 or 4 it does not matter.
in cumulative if today´s backup level is 2 (dont get confused by these numbers, they are simply used to compare) and yesterday was 1 then I will be copying changed blocks since yesterday, if instead I had a level 2 backup yesterday then I CANNOT backup changed blocks because today´s level 2 is not bigger than yesterday´slevel 2, instead I have to go further backwards until I find a level less than my today´s level
And Sybex book is wrong I guess because with three levels you cannot do much with backups, with 5 I can set incremental backups like
level 0 -- base backup
level 1 -- monthly backup
level 2 -- weekly backup
level 3 -- daily backup
level 4 -- hourly backup
-
To be honest I am thoroughly CONFUSED.
I don't know if I am troubling you with all my clouded understandings.
Originally posted by pando
I just made up for that Thursday level 1 backup, I can make it level 0, 2, or 3 or 4 it does not matter.
Do you mean to say that even if yesterday's is Level 2 and Level 2 blocks got changed, I can use any number and NOT necessarliy "3"??
Originally posted by pando
if instead I had a level 2 backup yesterday then I CANNOT backup changed blocks because today´s level 2 is not bigger than yesterday´slevel 2, instead I have to go further backwards until I find a level less than my today´s level
Here, my question is (and was): Since yesterday was Level 2 and that these Level 2 blocks got changed, why didn't you go far Level 3 to backup these changes??? Why make a Level 2 and backup Level 1 changes?
I mean, how will I then backup Yesterday's Level 2 changes, today?
Originally posted by pando
level 0 -- base backup
level 1 -- monthly backup
level 2 -- weekly backup
level 3 -- daily backup
level 4 -- hourly backup
To be honest, never understood the significance of this mapping...I mean why a "hourly" for Level 4 and not any other level?
Another question: As you said, even if it were 5 levels, lets say Level 4 blocks were changed yesterday and today I need to backup these "changed-Level 4 Blocks"; so what would my Level be then today?
Very sorry for all the queries, but honestly I think I will take the Oracle reference manual and go through again from the beginning.
-
if yesterday´s level was 2 and today I make it 3 if you like then is 3 bigger than 2? I would say yes for obvious reasons then if I want to perform
INCREMENTAL backup then all blocks changed since yesterday will be backedup
if I want to perform INCREMENTAL CUMULATIVE backup then I am able as well
if instead of 3 I use 2 I will be able to perform INCREMENTAL backup since 2 is bigger or equal to 2
BUT I wont be able to perform INCREMENTAL CUMULATIVE backup since 2 is NOT bigger than 2
It depends what you want to do, incremental or incremental cumulative, there are two types of incremental backups in RMAN
To be honest, never understood the significance of this mapping...I mean why a "hourly" for Level 4 and not any other level?
Now, we are talking about incremental backups here.
Level 4 has to go for hourly backup because my daily backup is level 3 and if I use level 2 instead of 4 for my hourly backup, is 2 bigger or equal than 3? No for obvious reasons so I cannot backup changed blocks since last level 3 backup (therefore we cannot call it hourly can we?), I would have to find the last backup which has the level smaller or equal to my current backup level
-
Code:
INCREMENTAL:
level 0
<------------------------------------------------------------
. . . . . . <---- . .
. . . . . <---- . . .
. . . . <---- . . . .
. <-------------------- . . . . .
. . <---- . . . . . .
. <---- . . . . . . .
level 0 2 2 1 2 2 2 0
sun mon tue wed thu fri sat sun
INCRMENTAL-CUMULATIVE:
level 0
<------------------------------------------------------------
. . . . <-------------------- . .
. . . . <------------ . . .
. . . . <---- . . . .
. <-------------------- . . . . .
. <------------ . . . . . .
. <---- . . . . . . .
level 0 2 2c 1 2c 2c 2c 0
sun mon tue wed thu fri sat sun
I am sure this is in the docs
[Edited by pando on 10-01-2002 at 09:55 AM]
-
I think a lot of things are clear now. I was not aware you were discussing "incremental" and "incremental-cumulative". I think "incremental" is what Sybex calls "incremental-diffrential".
Some points are clear now. I think, I also understood the importance of mapping (last paragraph).
But my last question is still unanswered - "As you said, even if it were 5 levels, lets say Level 4 blocks were changed yesterday and today I need to backup these "changed-Level 4 Blocks"; so what would my Level be then today?"
I would appreciate an answer for this last question. Anyway, I will get-on to do some serious reading again on this topic :-)
Many many thanks for your time and patience.
-
Originally posted by quester
But my last question is still unanswered - "As you said, even if it were 5 levels, lets say Level 4 blocks were changed yesterday and today I need to backup these "changed-Level 4 Blocks"; so what would my Level be then today?"
incremental backup then it has to be 4
and there is no such concept as level 4 blocks
look the figure I posted, it´s self clear, just that instead of having several levels there are only 3 in the figure
[Edited by pando on 10-01-2002 at 09:59 AM]
-
Originally posted by pando
incremental backup then it has to be 4
and there is no such concept as level 4 blocks
look the figure I posted, it´s self clear, just that instead of having several levels there are only 3 in the figure
[Edited by pando on 10-01-2002 at 09:59 AM]
Thanks a ton. I think I have understood. Your explanation and notes were very useful.
Posting Permissions
- You may not post new threads
- You may not post replies
- You may not post attachments
- You may not edit your posts
-
Forum Rules
|
Click Here to Expand Forum to Full Width
|
Reply With Quote