r12.2

[satish]

Hi Erman,

Have a Nice day

I need your help in understanding about  what is "Synchronizing snapshots" that happens during prepare phase and will it happen at file system level or database level?

Thanks,
Grill

[ErmanArslansOracleBlog]

It is filesystem snapshot.
We have seperate snapshots for each filesystem and these are maintained inside the database.
Snapshots  are current views of your filesystems. Basically, snapshot lists patches and versions of files in your filesystems.

[satish]

so if the snapshots are maintained in database,then the syncronising snapshots is also happens at tables right(database) that store the related information.

please correct me if wrong

Thanks,
Grill

[ErmanArslansOracleBlog]

It just happens .. The code ofcourse doesn't checking every file. So it uses some kind of lookup.
At the end of the day, the fs snapshot info is maintained in the database.

[satish]

Then what is flipping snapshots

Thanks,
Grill

[ErmanArslansOracleBlog]

Flipping snapshots? Where did you get this word? Any logs our outputs? Any document?

[satish]

During cutover phase,we will come across flipping snapshots

[ErmanArslansOracleBlog]

okay. You are talkin about ad_zd_adop.flip_snapshots.
It is probably a cutover thing in the manner of snapshots.
Like flipping the snapshots for run and patch filesystems.

But, need to check the code for ad_zd_adop.flip_snapshots, maybe there is a comment made there.

[Sri]

flipping snapshots means changing snapshot tables ad_snaphots,ad_files from one edition to other?is it right?can you give some idea

[ErmanArslansOracleBlog]

It just do the following update.
Note that I didn't include the select of that update, but it is clear that It flips the snapshot info in ad_snapshots. I mean it makes type C -> P and P -> C and G -> Q and Q -> G)

So, the same logic of the cutover applies for it as well..

update ad_snapshots
  set    snapshot_type=DECODE(snapshot_type, 'C', 'P', 'P', 'C',
                                            'G', 'Q', 'Q', 'G')

[satish]

What is  C, P, Q, G, can you please explain a little better

[ErmanArslansOracleBlog]

This is not documented in anywhere... I checked and asked, no info yet...
But, what I can say is;  C is the same as P and Q is the same as G ..
How can I think like this? Because as you see the following update , it sets C  to P and G to Q and vice versa.
Like fs1 and fs2 is the same, I believe "C and P" and "G and Q" are the same things . These are for cutover.. It changes the filesystems and it changes/cutovers the snapshot types accordingly (using these letters)...
This is what I think actually...

update ad_snapshots
  set    snapshot_type=DECODE(snapshot_type, 'C', 'P', 'P', 'C',
                                            'G', 'Q', 'Q', 'G')