Friday, July 11, 2014

Sample output from program to update data in Oracle shared memory.

Following is an example of updating Oracle data in shared memory.

From the database side we can see that only the data in SGA was changed, and the data on disk remained untouched.  (verified by flushing the buffer cache and forcing a re-read from disk)


CDB$ROOT@ORCL> create table test (text char(6));

Table created.

CDB$ROOT@ORCL> insert into test values ('vendor');

1 row created.

CDB$ROOT@ORCL> commit;

Commit complete.

CDB$ROOT@ORCL> select * from test;

TEXT
------
badguy

CDB$ROOT@ORCL> alter system flush buffer_cache;

System altered.

CDB$ROOT@ORCL> select * from test;

TEXT
------
vendor



Following is sample output from my program to update data in Oracle shared memory.  In this case it connected to every shared memory file in /dev/shm and replaced all strings "vendor" with "badguy".

[oracle@localhost shared_memory]$ ./sga_data_replace vendor badguy



WARNING WARNING WARNING


This program may crash or corrupt your Oracle database!!! It was written purely as an investigative tool and the author does not guarantee it will work, and does not recommend running it against PROD databases. Anyone may copy or modify the code provided.


USAGE :- sga_data_replace searchstring replacestring


Number of input parameters seem correct.
Length of search parameter vendor matches replace parameter badguy
This program will connect to all shared memory segments in /dev/shm belonging to all running databases on the server.
SEARCH FOR   :- vendor
REPLACE WITH :- badguy
Enter Y to continue :- Y
/dev/shm/ora_orcl_20381697_91 replace string at 366592
replace v with b
replace e with a
replace n with d
replace d with g
replace o with u
replace r with y
/dev/shm/ora_orcl_20381697_82 replace string at 3238216
replace v with b
replace e with a
replace n with d
replace d with g
replace o with u
replace r with y
/dev/shm/ora_orcl_20381697_75 replace string at 2230653
replace v with b
replace e with a
replace n with d
replace d with g
replace o with u
replace r with y
/dev/shm/ora_orcl_20381697_73 replace string at 1361711
replace v with b
replace e with a
replace n with d
replace d with g
replace o with u
replace r with y
/dev/shm/ora_orcl_20381697_73 replace string at 1361718
replace v with b
replace e with a
replace n with d
replace d with g
replace o with u
replace r with y
/dev/shm/ora_orcl_20381697_62 replace string at 1081334
replace v with b
replace e with a
replace n with d
replace d with g
replace o with u
replace r with y
Error: File is empty, nothing to do