Expert Oracle Exadata - Parent Directory

CHAPTER 10 EXADATA WAIT EVENTSreliable messageThe reliable message event is used to record time spent communicating with background processes,like the checkpoint process (CKPT). We have included it here because of its close association with theenq: KO – fast object checkpoint event.Event MeaningThis event is the precursor to the enq: KO – fast object checkpoint event (among others). Thecommunication is done using an inter-process communication channel rather than a more normal postmechanism. This communication method allows the sender to request an ACK before it continues, thusthe reason it is called a reliable message. It is generally a very short duration event as it only records timefor communicating between processes. Both the users foreground process and the chkpt process willwait on this event as they communicate with each other. Here’s an excerpt of a 10046 trace file showing acomplete reliable message event:PARSING IN CURSOR #46963980936744 len=50 dep=0 uid=0 oct=3 lid=0 tim=1301885220743528hv=3032626544 ad='2cf675ff0' sqlid='7y09dtyuc4dbh'select avg(pk_col) from kso.skew2 a where col1 > 0END OF STMTPARSE#46963980936744:c=1999,e=2122,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=1,plh=2117817910,tim=1301885220743527WAIT #46963980936744: nam='reliable message' ela= 1360 channel context=11888341784 channelhandle=12088585896 broadcast message=12089037216 obj#=75759 tim=1301885220745397WAIT #469: nam='enq: KO - fast object checkpoint' ela= 183 ... obj#=75759 tim=130WAIT #469: nam='enq: KO - fast object checkpoint' ela= 144 ... obj#=75759 tim=130WAIT #469: nam='enq: PS - contention' ela= 200 ... obj#=75759 tim=130WAIT #469: nam='os thread startup' ela= 58333 p1=0 p2=0 p3=0 obj#=75759 tim=130WAIT #469: nam='os thread startup' ela= 101705 p1=0 p2=0 p3=0 obj#=75759 tim=130WAIT #469: nam='enq: PS - contention' ela= 276 ... obj#=75759 tim=130WAIT #469: nam='os thread startup' ela= 102988 p1=0 p2=0 p3=0 obj#=75759 tim=130WAIT #469: nam='os thread startup' ela= 103495 p1=0 p2=0 p3=0 obj#=75759 tim=130WAIT #469: nam='enq: PS - contention' ela= 237 ... obj#=75759 tim=130WAIT #469: nam='os thread startup' ela= 102655 p1=0 p2=0 p3=0 obj#=75759 tim=130WAIT #469: nam='os thread startup' ela= 102329 p1=0 p2=0 p3=0 obj#=75759 tim=130WAIT #469: nam='enq: PS - contention' ela= 313 ... obj#=75759 tim=130WAIT #469: nam='os thread startup' ela= 102673 p1=0 p2=0 p3=0 obj#=75759 tim=130ParametersHere are the parameters for the reliable message event.P1 - channel contextP2 - channel handleP3 - broadcast messageobj# - The object number of the object of interest (not always set)340