Kevin Kempf's Blog

April 3, 2009

RMAN and Advanced Compression

Filed under: Oracle, RMAN — Tags: — kkempf @ 11:03 am

Since we’d purchased 11g Advanced Compression, I thought I’d compare the new ZLIB compression algorithm to the existing BZIP2 algorithm in RMAN.  As a reminder, Oracle licensing prevents you from using ZLIB unless you’ve purchased Advanced Compression, and the RDBMS compatible init parm must be set to 11.0.0 or higher.  In a nutshell, ZLIB compresses less, uses less CPU, and is faster, while bzip2 compresses better, CPU is noticeable, and it’s slow.  ZLIB seems like a good middle-ground (between no compression and BZIP2), though I have no idea why Oracle decided they need to charge you to use it.

The RMAN syntax is simple:

configure compression algorithm ‘ZLIB’;

configure compression algorithm ‘BZIP2’;

configure compression algorithm clear;

working with CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO COMPRESSED BACKUPSET;

The performance I saw was ZLIB was 15% faster, and 16% larger in output size when I ran a full backup of my EM repository (to disk)

Total Time Input Size Output Size Output Rate
BZIP2 214sec 4.7gb 664.1mb 3.1mb/s
ZLIB 179sec 5.62gb 1.07gb 6.12mb/s
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