db file parallel read :
It has no relation with parallel read and parallel DML,It just appear in that priod when doing recover and some server process read noncontinue oracle blocks within one or more datafiles.
db file parallel write :
it has no relation with parallel write,just write dirty buffers to datafiles by dbwr process,but in async mode ,it will not wait the batch writing action must be completed all,it will push the buffer back in LRU list.
db file single write:
the event often occured when the ckpt update the head of datafile.
direct path read:
when read data into PGA,this event will happen.read behaviour mode is async mode or sync mode.it is determined by the value of disk_async_io.This action often used in reading temporary segment including soring,parallel query and hash_join.if async read is available, many process will be done for request and continue to deal the buffer in PGA
direct path write:
write data buffers from pga to datafiles.it is often happenning when direct load
by insert with append hint ,CTAS,and other DML operations.
log file parallel write:
when using async mode to refresh log buffer to logfile.
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