Hi tolga,
Unline parallel queries & INSERT's, I think its not possible for
parallel UPDATE's and DELETE's to do direct read's.
Lets take this scenario.
We are updating a 1000 block table in parallel. (lets say we are
updating column A)
If oracle is doing direct read's that means the blocks will be read
direclty into the PGA instead of the buffer cache.
One of the parallel process is updating block 200.
It updated row 1 and while updating row 2 it sees that the row is
locked by another transaction (T2) from another session
Now lets say that transaction T2 updated column B in row 2 of block
200.
Lets say after some time T2 commits.
Now if direct read occurs for the block how does oracle deal with this
scenario ?
Now all blocks are read in current mode (as it is a DML)
There is one version of the block in the PGA of the parallel process
that has row 1 modified.
We have one version in the buffer cache that has row 2 modified.
regards
srivenu
Received on Tue Nov 08 2005 - 10:13:20 CST
