RMAN Tips: Test Plan to identify correct number of channels for RMAN compressed backups optimal performance (Doc ID 1435723.1)

Purpose

Tuning RMAN compressed backups for performance and balance IO.

Scope

Increasing the number of channels increases the number of CPU cores available to execute the compression.
Rules of thumb -

1. Don't leave a lot of free space in the tablespaces. Free space is read but not written.

2. ASM to ASM tune the RMAN backup buffers. (On 11g Buffers are optimized on ASM )

3. With BIGFILES use "SECTION SIZE" not MAXPIECESIZE. The difference is MAXPIECESIZE will serialize the backup of all files assigned to a given channel. Using "SECTION SIZE" any files larger than the section value multiple channel can backup a single file in parallel improving the performance for IO and compression.

4. Determine the CPU core number and use that for the max channels that can be allocated. We are looking for the point of diminished return. Afterwards you must verify it's not impacting production IO and scale the changes back from there as required.

Details