Re: Block Identifiers in Multitenant Databases

Sorry,
I didn't intend my previous reply to go to the individual rather than the group.

I've just done
od -o {filename} | head -64 on the system tablespace file for the root, seed and pdb of a multi tenant database. Then I've flagged each line of the file (changed the first space in each line to a letter surrounded by spaces).
The sorted the three files together.

In v$datafile root system is file 1, seed system is file 5, and the pdb system is file 11.
The following may be a coincidence (the first 6 digit number is the byte number in the file, in Octal:

0020060 p 020000 000000 000011 000003 000000 000000 000000 000000

    prod system = file# 9
0020060 r 020000 000000 000001 000003 000000 000000 000000 000000

    root system = file# 1
0020060 s 020000 000000 000005 000003 000000 000000 000000 000000

    Seed system = file# 5

Note the value of byte 002065

Regards
Jonathan Lewis

On Wed, 6 Oct 2021 at 10:03, Jonathan Lewis <jlewisoracle_at_gmail.com> wrote:

> Where are you starting from that gives you the RDBA ?
>
> I don't think that there's anything in the block that identifies the
> CON_ID/pdb id, but when Oracle is handling the block it has the relative
> file number, tablespace number and absolute file number of the block in the
> block handle structure (x$bh), and two of those three would have been
> derived (or deduced) information. WIth the absolute file number you just
> need to check v$datafile to identify the container. Bottom line - if you
> can infer the tablespace number you're done.
>
> Brute force method: check v$datafile for every absolute file# that matches
> your relative file number (which isn't goint to eliminate many pdbs if
> you're using bigfile tablespaces across the board), then dump the matching
> block number from each file. (That's if you really want to find out for
> the occasional special case, but probably too much of a nuisance in
> general).
>
> Regards
> Jonathan Lewis
>
> On Tue, 5 Oct 2021 at 20:29, Seth Miller <sethmiller.sm_at_gmail.com> wrote:
>
>> I am attempting to isolate the identification attributes of an individual
>> block. Prior to multitenant, this was easy to do using the RDBA to get the
>> file and block. However, in a PDB, the RDBA does not tell me how the root
>> container identifies the block either by the file number at the root level
>> or by the container ID.
>>
>> I've done a lot of digging and debugging and can't figure out how the
>> root container identifies a block or where it might be in the block header.
>> Any help would be appreciated.
>>
>> Seth
>>
>

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