Both actually. Oracle suggests to set the parallelism (# of channels) for
the sbt device to match the number of physical tape devices. Disable media
management multiplexing because RMAN intelligently takes care of the
multiplexing.
If the throughput is too low, adjustments on the RMAN side (multiplexing
level, buffer size, number of buffers) can increase the amount of data
coming into the media manager.
Yes, a tape device refers to the media management library you have
configured in RMAN. You can have multiple physical tapes receiving data
through that single RMAN tape device.
On Mon, Aug 1, 2016 at 11:46 AM, Chris Taylor <
christopherdtaylor1994@xxxxxxxxx> wrote:
Ok, I'm confused by the following:
Oracle suggests that no more than 1 channel be used per tape device toprevent inefficient writes and shoe-shining.
*> "Do not utilize media management multiplexing (multiple channels per
tape drive). RMAN backup pieces will not be efficiently restored due to the
interleaving of pieces on the same tape volume, which may necessitate the
forward and *
*> backward movement of the tape."*
It seems like you're saying don't allocate more than one RMAN channel per
tape device, but the quote seems to be saying don't utilize hardware
multiplexing channels per tape drive (Which is what I think our backup guy
is actually suggesting we do).
One more question: I assume a "tape device" (in general) contains multiple
tapes that are loaded and available for writing?
Chris
On Mon, Aug 1, 2016 at 11:36 AM, Seth Miller <sethmiller.sm@xxxxxxxxx>
wrote:
Duplexing wouldn't make much sense since that would mean copying the same
file to multiple destinations. He is probably referring to multiplexing or
parallelism. There is a difference between RMAN multiplexing and
parallelism and the term "stream" usually relates to the latter. RMAN
multiplexing allows multiple files to be read at the same time within a
single channel and defaults to 8. RMAN parallelism refers to multiple
channels writing to the same destination and is often referred to as
multiplexing on the media management side.
Oracle suggests that no more than 1 channel be used per tape device to
prevent inefficient writes and shoe-shining.
*"Do not utilize media management multiplexing (multiple channels per
tape drive). RMAN backup pieces will not be efficiently restored due to the
interleaving of pieces on the same tape volume, which may necessitate the
forward and backward movement of the tape."*
Seth Miller
