Testing rman recovery from block corruption in an 11g ASM environment
- From: hpuxrac <johnbhurley@xxxxxxxxxxxxx>
- Date: Sun, 22 Mar 2009 16:08:07 -0700 (PDT)
Disclaimer and caveat:
Testing database recoveries is a DBA responsibility. Each time you
migrate environments this really must be done ... you don't want to be
in a place where you tell management ... well the last time we tried
this ... several years ago on a different os ... different oracle
release ... different storage ... it worked ok.
Corrupting database blocks on purpose ... to setup a database recovery
attempt ... is really something that goes kind of above and beyond
normal recovery testing. After all ... if you want to believe
oracle ... it should all be working right? In my mind however ... you
really should test this from time to time.
Obviously testing like this can cause problems real problems so before
you attempt something like this you want to have good backups and
perform your first sets of testing on a test throwaway type of
database before thinking about doing testing on anything more than
test type system.
So anyways ... when you are thinking about intentionally damaging
blocks in the database ASM throws some more wrinkles in the mix. Most
of my environments I have run using RAW and to damage blocks in an
environment like that dd is the tool of choice usually ... it just
gets a little tricky at times in a RAW environment figuring out
offsets and how many blocks to skip before throwing the old /dev/zero
hammer down.
At some point I will write up what I found about the additional
complications in testing this kind of thing in an ASM environment
( probably into a word document ) ... including specific commands
etc. If you want the writeup please let me know by direct email.
Here's my quick overview of one way this can be tested in an ASM
environment. ( My environment was 64 bit OEL 5.1 using 11.1.0.7
database and ASM instance on EMC Clariion )
1) Have an rman disk backup available and a database in archivelog
mode using ASM
2) create a small tablespace ( MINI ) in ASM
3) create a table in the new tablespace and insert some rows in it
( maybe ( col1 char(2000), col2 char(2000) col3 char(2000) so each row
is in a separate block ) then commit.
4) Get a new incremental that updates the previous one ( will get a
new base copy of the new tablespace ).
5) Take the new tablespace offline
6) Use asmcmd cp command to copy the new tablespace to a file system.
7) Use some kind of hex editor to damage one or more of the blocks in
the copy of the tablespace in the file system ( missed my old dd
command here but maybe you can do it with dd? ).
8) Use asmcmd cp command to put the copied tablespace back into
diskgroup.
*** Note that at this point there will be 2 versions of the datafile
for the new tablespace in ASM. Limitations currently on copying back
in using asmcmd force you to do something like this ... ( you cannot
put the whole MINI.266.882111791 enchilada directly back into ASM via
asmcmd cp ).
asmcmd <<EOF
cp -f /home/oracle/temp_rec/MINI.266.682111791 +PROD_DG1/prod/
datafile/MINI
exit
9) Now you have to alter to fix the name of the datafile ... something
like ...
ALTER TABLESPACE MINI RENAME datafile '+DISKGROUPNAME/ORACLE_SID/
datafile/MINI.266.68211179
1' to '+DISKGROUPNAME/ORACLE_SID/datafile/MINI.268.682115173';
10) alter the tablespace back online
11) switch logfiles ( why not )
12) try to do an rman backup or validate ... should get errors if you
whacked MINI correctly ...
*** Should be able to use various views to see what blocks rman ( or
validate ) has flagged ...
13) rman ... one way is blockrecover corruption list
Sorry this posting is so long but thought it would be good to have
something out somewhere. I thought it would be easy to locate someone
else's step by step guide to testing block recovery in an ASM
environment but I did not find much readily available or at least
bailed out and decided to figure out steps in detail myself.
There's probably some other better ways of doing this ... it is pretty
cumbersome to offline it .. asmcmd cp it out ... damage it ... cp it
back in ... alter tablespace it ... and online it ... but my procedure
does work.
.
- Prev by Date: composite primary key vs. primary key on additional single column
- Next by Date: How to pass Oracle certification exam?
- Previous by thread: composite primary key vs. primary key on additional single column
- Next by thread: How to pass Oracle certification exam?
- Index(es):
Relevant Pages
|
