1 ) Can anyone explain the concepts of redo copy and redo allocation.
2 ) Where is the SCN # located in the control file and can we view this after the command alter database backup controlfile to trace.
These two are latches. When Server Process needs to transfer data buffers into log buffers. It gets redo copy latche. After getting this latche, it tries to get redo allocation latche. When It get that, It can transfer the blocks into log bufers. After completion of transformation, it releases the redo allocation latche. After releasing the redo allocation latche, It can release the redo copy latche.
There is only one redo allocation lache per Instance per Database.
There is one redo copy latche per Server Process.