Re: student question: incremental backups (level 0 and level 1)
Date: Thu, 26 Jun 2008 11:11:42 -0700 (PDT)
Message-ID: <310faf59-f328-46f3-9c01-fd1fb477167d@34g2000hsf.googlegroups.com>
On Jun 26, 4:16 am, pellicleund..._at_hotmail.com (obakesan) wrote:
> Hi
>
> ok ... things are gradually being revealed ...
>
> In article <lkm664900qskls1v784bq0qug68odsk..._at_4ax.com>, sybra..._at_hccnet.nl
> wrote:
>
> >On Thu, 26 Jun 2008 04:57:54 GMT, pellicleund..._at_hotmail.com
> >(obakesan) wrote:
>
> >>so perhaps a level 0 is as near as damit a full tablespace copy ...
>
> >It is not.
> >'Empty' blocks will not be copied. Empty blocks means blocks without a
> >SCN. A block which has been used at least once has a SCN and will be
> >copied.
>
> so then, does this SCN get updated or invalidated at say a truncate table?
>
> See Ya
> (when bandwidth gets better ;-)
>
> Chris Eastwood
> Photographer, Programmer Motorcyclist and dingbat
> blog:http://cjeastwd.blogspot.com/
>
> please remove undies for reply
Sybrand is right as usual.
http://www.jlcomp.demon.co.uk/faq/blockdump.html
Note you can do things like
SQL> create table jjjjj as select * from all_objects;
Table created.
SQL> connect / as
sysdba
Connected.
SQL> select file_id,block_id from dba_extents where
segment_name='JJJJJ';
FILE_ID BLOCK_ID
---------- ----------
64 91297 64 91305 64 91313 64 91321 64 91329 64 91337 64 91345 64 91353 64 91361 64 91369 64 91377
FILE_ID BLOCK_ID
---------- ----------
64 91385 64 91393 64 122761 64 122769 64 122777 64 121993 64 122121 64 122249
19 rows selected.
SQL> connect rossjeg
Enter password:
Connected.
SQL> truncate table jjjjj;
Table truncated.
SQL> connect / as sysdba;
Connected.
SQL> select file_id,block_id from dba_extents where
segment_name='JJJJJ';
FILE_ID BLOCK_ID
---------- ----------
64 91297
SQL> alter system dump datafile 64 block 122249;
System altered.
Then you can examine the data block in the trace in your user_dump_dest and see that it does indeed have an SCN:
...
*** 2008-06-26 10:55:47.751
*** SESSION ID:(15.3619) 2008-06-26 10:55:47.700
Start dump data blocks tsn: 15 file#: 64 minblk 122249 maxblk 122249
buffer tsn: 15 rdba: 0x1001dd89 (64/122249)
scn: 0x0000.1a7c00a8 seq: 0x02 flg: 0x04 tail: 0x00a80602
frmt: 0x02 chkval: 0x8f10 type: 0x06=trans data
Block header dump: 0x1001dd89
Object id on Block? Y
seg/obj: 0x28d9e csc: 0x00.1a7c0071 itc: 3 flg: - typ: 1 - DATA
fsl: 0 fnx: 0x0 ver: 0x01
...
I wouldn't know whether this applies in every situation like after a shrink in ASSM...
Richard Foote's blog has (and some other places have) good examples of how to interpret dumps.
jg
-- @home.com is bogus. "So what do they call this generation that is now between 16 and 27?" "It's a word that starts with F and ends with D." "Generation FRED?" - heard on radioReceived on Thu Jun 26 2008 - 13:11:42 CDT