RE: RMAN question(s)

In case anyone is interested - I did a test of the 10g "as compresssed" backupset on a 285GB databases and here are the results:

W/O Compression: backup size = 280GB, backup time = 2 to 10 hours with an average of about 7.5 hours over the past 3 months (this goes to a disk staging area and later to tape on a Netbackup server with a LOT of other backup activity so there is a wide variance in backup times depending on what else is running at the same time)

W/ Compression: backup size = 36GB, backup time = 2.9 hours (only tested once so far)

So, I can't really make any conclusions on the backup time yet due to the large variance in backup times on this environment, but it's clear that the space savings was significant (280-36=244 & 244/280=87% reduction) and the runtime from this one sample was close to the bottom of the normal range so that's promising.

Here are the details of the test environment: AIX 5.3, Oracle 10.2.0.2, Netbackup 5.1 MP4, BaanIV ERP application data

Regards,
Brandon

Here is the raw data:

SQL> select handle, status, start_time, round(elapsed_seconds/60/60,1) HRS, round(bytes/1024/1024/1024) GB, compressed from v$backup_piece where start_time > sysdate-90 order by 3

HANDLE                                   S START_TIME             HRS

---------------------------------------- - --------------- ----------
---------- ---
baantest_db_3_1_627820117                A 13-JUL-07 10:28        1.8
88 NO
baantest_db_4_1_627820117                A 13-JUL-07 10:28        1.8
90 NO
baantest_db_2_1_627820117                A 13-JUL-07 10:28        1.8
91 NO
c-1234567890-20070713-00                 A 13-JUL-07 12:17          0
0 NO
baantest_db_14_1_628542124               A 21-JUL-07 19:02        9.2
90 NO
baantest_db_12_1_628542123               A 21-JUL-07 19:02        9.2
88 NO
baantest_db_13_1_628542124               A 21-JUL-07 19:02        9.2
91 NO
c-1234567890-20070722-00                 A 22-JUL-07 04:15          0
0 NO
baantest_db_16_1_629147088               A 28-JUL-07 19:04        8.9
88 NO
baantest_db_18_1_629147089               A 28-JUL-07 19:04          9
90 NO
baantest_db_17_1_629147088               A 28-JUL-07 19:04          9
91 NO
c-1234567890-20070729-00                 A 29-JUL-07 04:06          0
0 NO
baantest_db_20_1_629751899               A 04-AUG-07 19:05        9.5
88 NO
baantest_db_22_1_629751899               A 04-AUG-07 19:05        9.7
90 NO
baantest_db_21_1_629751899               A 04-AUG-07 19:05        9.7
91 NO
c-1234567890-20070805-00                 A 05-AUG-07 04:48          0
0 NO
baantest_db_24_1_630356804               A 11-AUG-07 19:06        8.9
88 NO
baantest_db_26_1_630356804               A 11-AUG-07 19:06        9.1
90 NO
baantest_db_25_1_630356804               A 11-AUG-07 19:06        9.1
91 NO
c-1234567890-20070812-00                 A 12-AUG-07 04:12          0
0 NO
baantest_db_28_1_630961744               A 18-AUG-07 19:09        9.8
88 NO
baantest_db_30_1_630961744               A 18-AUG-07 19:09         10
90 NO
baantest_db_29_1_630961744               A 18-AUG-07 19:09         10
91 NO
c-1234567890-20070819-00                 A 19-AUG-07 05:07          0
0 NO
baantest_db_32_1_631566616               A 25-AUG-07 19:10        6.2
88 NO
baantest_db_34_1_631566616               A 25-AUG-07 19:10        6.2
91 NO
baantest_db_33_1_631566616               A 25-AUG-07 19:10        6.3
91 NO
c-1234567890-20070826-00                 A 26-AUG-07 01:26          0
0 NO
baantest_db_36_1_632171576               A 01-SEP-07 19:12        9.2
91 NO
baantest_db_37_1_632171576               A 01-SEP-07 19:12        9.1
87 NO
baantest_db_38_1_632171576               A 01-SEP-07 19:12        9.2
91 NO
c-1234567890-20070902-00                 A 02-SEP-07 04:27          0
0 NO
baantest_db_40_1_632776372               A 08-SEP-07 19:12        3.5
89 NO
baantest_db_42_1_632776373               A 08-SEP-07 19:12        3.6
91 NO
baantest_db_41_1_632776372               A 08-SEP-07 19:12        3.6
91 NO
c-1234567890-20070908-00                 A 08-SEP-07 22:47          0
0 NO
baantest_db_45_1_633380855               A 15-SEP-07 19:07        2.8
11 YES
baantest_db_44_1_633380854               A 15-SEP-07 19:07        2.9
12 YES
baantest_db_46_1_633380855               A 15-SEP-07 19:07        2.9
13 YES
c-1234567890-20070915-00     

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Allen, Brandon

Hi Robert, could you please clarify a couple things for me since I've never tried compressed backupsets?

1. My understanding is that "as compressed backupset" is not recommended if you're backing up to a tape drive (e.g. LTO3) that is already performing its own compression. Is that correct?
2. You say compression will save time as well, but I thought that a compressed backup would actually take longer due to the extra processing required for the compression.

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