>I have a dedicated disk pool for one specific Oracle RMAN backup
>using 8 channels of a database at 300Gb. The backup takes about 2
>hours, but if I clean the cache on the pool, I will see no storage
>space usage until the channel session has ended. So, at the end of
>the backup, the storage pool usage will go from 0% to about 66%. My
>storage pool size is 310Gb and I don't enable compression. Two
>questions :
>
>1) What is TSM doing with each channel's data being sent ? Is it
>buffering it somehow ?

Most of the TSM queries relating to storage use are blind to files
in transit. For example, when an offsite tape reclamation at our site
copies an 8 gigabyte file, we see no change in the percentage
utilization of the output tape until the entire file is moved, at
which point the utilization suddenly goes up by about 40%. I
suspect that you are seeing a similar phenomenon.