Direct I/O - what is it?

[roukie_dba]

Gurus/Members

I have heard the term 'direct I/O' used quite a lot in oracle running on unix platforms.

1) Please explain in detail, if possible, what direct I/O means, and,

2) What are the advantages and disadvantages of it?

3) Any related white papers?

Thanks

[dinocwh]

that's my understanding...

direct io is a way for bypassing the kernal cache for files which means that physical read/write should be done for data.

advs. is... it is no meaning for caching a huge file that is usually be used under a datawarehouse environment. take the cache memory for other process may benifit more to the system... say... parallel processes on seaching data

disadvs... obversious... small cacheable file can't be cached..

white paper... ... i like to take a look also