Tag: RMAN

Hi all!
Again talking about cloud backups for on-premise databases: An important aspect is to compress the data, so network consumption might be reduced once less data is being transfered.
It’s also important to evaluate CPU consumption. As higher compress algorithm is, as much CPU it uses. So, pay attention!

Now, how to choose the compression algorithm? Here the options Oracle give us:

SQL> col ALGORITHM_NAME for a15
set line 200
SQL> select ALGORITHM_NAME,INITIAL_RELEASE,TERMINAL_RELEASE,ALGORITHM_DESCRIPTION,ALGORITHM_COMPATIBILITY  from v$rman_compression_algorithm;
ALGORITHM_NAME INITIAL_RELEASE    TERMINAL_RELEASE   ALGORITHM_DESCRIPTION                                            ALGORITHM_COMPATIB
-------------- ------------------ ------------------ ---------------------------------------------------------------- ------------------
BZIP2          10.0.0.0.0         11.2.0.0.0         good compression ratio                                           9.2.0.0.0
BASIC          10.0.0.0.0                            good compression ratio                                           9.2.0.0.0
LOW            11.2.0.0.0                            maximum possible compression speed                               11.2.0.0.0
ZLIB           11.0.0.0.0         11.2.0.0.0         balance between speed and compression ratio                      11.0.0.0.0
MEDIUM         11.2.0.0.0                            balance between speed and compression ratio                      11.0.0.0.0
HIGH           11.2.0.0.0                            maximum possible compression ratio                               11.2.0.0.0

How to identify our compression algorithm?

RMAN> show COMPRESSION ALGORITHM;
RMAN configuration parameters for database with db_unique_name EZM_PRFL are:
CONFIGURE COMPRESSION ALGORITHM 'BASIC' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE ; # default

And how to change it?

RMAN> CONFIGURE COMPRESSION ALGORITHM 'HIGH';
new RMAN configuration parameters:
CONFIGURE COMPRESSION ALGORITHM 'HIGH' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE;
new RMAN configuration parameters are successfully stored
RMAN> show COMPRESSION ALGORITHM;
RMAN configuration parameters for database with db_unique_name EZM_PRFL are:
CONFIGURE COMPRESSION ALGORITHM 'HIGH' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE;

Ok,
But how to evaluate my compression ratio?

See the difference between INPUT_BYTES_DISPLAY and OUTPUT_BYTES_DISPLAY columns from the query:

prddb> col STATUS for a10
prddb> col INPUT_BYTES_DISPLAY for a15
prddb> col OUTPUT_BYTES_DISPLAY for a15
prddb> col TIME_TAKEN_DISPLAY for a20
prddb> SELECT SESSION_KEY,
2         INPUT_TYPE,
3         STATUS,
4         TO_CHAR(START_TIME, 'mm/dd/yy hh24:mi') start_time,
5         TO_CHAR(END_TIME, 'mm/dd/yy hh24:mi') end_time,
6  --       ELAPSED_SECONDS / 3600 hrs,
7         COMPRESSION_RATIO,
8         INPUT_BYTES_DISPLAY,
9         OUTPUT_BYTES_DISPLAY,
10         TIME_TAKEN_DISPLAY
11    FROM V$RMAN_BACKUP_JOB_DETAILS
12    where input_type like 'DB%'
13   ORDER BY SESSION_KEY
14  /SESSION_KEY INPUT_TYPE    STATUS     START_TIME     END_TIME       COMPRESSION_RATIO INPUT_BYTES_DIS OUTPUT_BYTES_DI TIME_TAKEN_DISPLAY
----------- ------------- ---------- -------------- -------------- ----------------- --------------- --------------- --------------------
          2 DB FULL       COMPLETED  04/22/16 12:59 04/22/16 13:06        6,84838963     4.26G         636.50M       00:06:57
          9 DB FULL       COMPLETED  04/22/16 13:47 04/22/16 13:54        6,83764706     4.26G         637.50M       00:06:37
         14 DB FULL       COMPLETED  04/22/16 16:26 04/22/16 16:33        6,84189878     4.26G         637.25M       00:06:48

KB: https://docs.oracle.com/cd/E11882_01/backup.112/e10642/rcmconfa.htm#BRADV89466

Done?
If you have any question, please let me know in the comments! 😉
Matheus.