Non-recursive and recursive cpu and elapsed time in extended SQL trace files are distinguished by whether the “dep=” value for PARSE, EXEC and FETCH statements is zero (i.e. non-recursive) or greater than zero (i.e. recursive). Millsap and Holt in Optimizing Oracle Performance [Pgs. 90-94] do an excellent job explaining the differentiation, and it is important in profiling resource time since all recursive time is invoked by non-recursive parent statements. What is typically not discussed, and is a little more complicated to categorize, is something called exclusive time. Exclusive time is simply the time that can be directly attributed to executing a particular PARSE, EXEC or FETCH statement. In other words it is the statement time less any recursive time incurred for that statement. It’s actually a little more complicated in that what we really have for each motivating statement is four time categories, the exclusive time for that statement and any recursive PARSE, EXEC or FETCH time. However, this is a recursive, no pun intended, relationship for each recursive PARSE, EXEC or FECTH statement since they may also have recursive children. In order to make the time accounting a little easier I wrote what I call an “execution tree” for PARSE, EXEC or FETCH statements in a trace file. It basically creates an indented tree listing based on recursive level and sums the four types of time when a parent recursive level is reached. This makes it much easier to determine the proper time accounting.
Partial trace file:
=====================
PARSING IN CURSOR #4 len=740 dep=1 uid=61 oct=3 lid=61 tim=1220394068956400 hv=1020616855 ad='e3eaf9e0'
select tab.row_id, tab.msgid, tab.corrid, tab.priority, tab.delay, tab.expiration, tab.retry_count, tab.exception_qschema, tab.exception_queue, tab.chain_no, tab.local_order_no, tab.enq_time, tab.time_manager_info, tab.state, tab.enq_tid, tab.step_no, tab.sender_name, tab.sender_address, tab.sender_protocol, tab.dequeue_msgid, tab.user_prop, tab.user_data from "AE2"."AQ$_ANALYSIS_ENGINE_IN_F" tab where (subscriber_id = :1 and subscriber_name = :2 and queue_evtid = :3 and delivery_mode = 'PERSISTENT') and (tab.user_data.extract('/ns:NIFMessage/ns:payload/aee:analysisSequenceId', 'xmlns:ns="http://nif.llnl.gov" xmlns:aee="http://www.oracle.com/aq/XMLType"').getStringVal() like '%TAS_WFLZfocusToTCC_Sequencer%')
END OF STMT
EXEC #4:c=0,e=626,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394068956393
FETCH #4:c=69989,e=68532,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069024985
WAIT #6: nam='Streams AQ: waiting for messages in the queue' ela= 147396 queue id=73580 process#=4038849208 wait time=1 obj#=-1 tim=1220394069172592
EXEC #4:c=0,e=317,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069173174
FETCH #4:c=71990,e=70466,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069243668
ERROR #6:err=25228 tim=783947179
WAIT #6: nam='SQL*Net break/reset to client' ela= 6 driver break?=1 p3=0 obj#=-1 tim=1220394069244129
WAIT #6: nam='SQL*Net break/reset to client' ela= 271 driver break?=0 p3=0 obj#=-1 tim=1220394069244422
WAIT #6: nam='SQL*Net message to client' ela= 2 driver #bytes=1 p3=0 obj#=-1 tim=1220394069244444
WAIT #6: nam='SQL*Net message from client' ela= 807 driver #bytes=1 p3=0 obj#=-1 tim=1220394069245294
=====================
PARSING IN CURSOR #6 len=174 dep=0 uid=61 oct=47 lid=61 tim=1220394069245484 hv=562127231 ad='ef4b8648'
begin dbms_aqin.aq$_dequeue_in( :1, :2, :3, :4, :5, :6, :7, :8, :9, :10, :11, :12, :13, :14, :15, :16, :17, :18, :19, :20, :21, :22, :23, :24, :25, :26, :27, :28, :29); end;
END OF STMT
PARSE #6:c=0,e=38,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,tim=1220394069245479
EXEC #4:c=0,e=284,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069247543
FETCH #4:c=73988,e=72207,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069319777
EXEC #4:c=0,e=291,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069320320
WAIT #4: nam='latch: cache buffers chains' ela= 41 address=3983055408 number=122 tries=0 obj#=-1 tim=1220394069344643
FETCH #4:c=71989,e=70324,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069390667
WAIT #6: nam='Streams AQ: waiting for messages in the queue' ela= 978084 queue id=73580 process#=4038849208 wait time=1 obj#=-1 tim=1220394070368953
EXEC #4:c=0,e=322,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394070369487
FETCH #4:c=71990,e=70318,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394070439833
EXEC #6:c=220966,e=1194523,p=0,cr=1896,cu=0,mis=0,r=0,dep=0,og=1,tim=1220394070440145
Resulting execution tree:
Line 39: EXEC #4:c=0,e=626,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394068956393,hv=1020616855
Line 40: FETCH #4:c=69989,e=68532,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069024985,hv=1020616855
Line 42: EXEC #4:c=0,e=317,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069173174,hv=1020616855
Line 43: FETCH #4:c=71990,e=70466,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069243668,hv=1020616855
PARSE: cpu= 0 ela= 0
EXEC: cpu= 0 ela= 943
FETCH: cpu= 141979 ela= 138998
Recursive: cpu= 141979 ela= 139941; Exclusive: cpu= -141979 ela= -139903
Line 53: PARSE #6:c=0,e=38,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,tim=1220394069245479,hv=562127231
Line 54: EXEC #4:c=0,e=284,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069247543,hv=1020616855
Line 55: FETCH #4:c=73988,e=72207,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069319777,hv=1020616855
Line 56: EXEC #4:c=0,e=291,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069320320,hv=1020616855
Line 58: FETCH #4:c=71989,e=70324,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394069390667,hv=1020616855
Line 60: EXEC #4:c=0,e=322,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394070369487,hv=1020616855
Line 61: FETCH #4:c=71990,e=70318,p=0,cr=630,cu=0,mis=0,r=0,dep=1,og=1,tim=1220394070439833,hv=1020616855
PARSE: cpu= 0 ela= 0
EXEC: cpu= 0 ela= 897
FETCH: cpu= 217967 ela= 212849
Recursive: cpu= 217967 ela= 213746; Exclusive: cpu= 2999 ela= 980777
Line 62: EXEC #6:c=220966,e=1194523,p=0,cr=1896,cu=0,mis=0,r=0,dep=0,og=1,tim=1220394070440145,hv=562127231
PARSE: cpu= 0 ela= 38
EXEC: cpu= 220966 ela= 1194523
FETCH: cpu= 0 ela= 0
As you can see, when you “go up a recursive level” the PARSE, EXEC and FETCH totals of the previous level are summed by category, totaled as recursive time, and the resulting exclusive time based on the parent statement’s time.
This whole concept of exclusive time becomes important when considering how to most accurately reflect “interval” time in the trace event timeline. My first attempt at categorizing time depended on only using non-recursive totals, that is recursive depth zero, PARSE, EXEC and FETCH statements along with event elapsed time. This had the convenience of not requiring complicated tracking of all the recursive time allocations, and with the proper disclosure was a perfectly valid method of creating the timeline. Of course there are some problems with only representing recursive depth zero time, the biggest one being tracing applications that are predominantly PL/SQL activity. This can lead to few, if any, recursive depth zero timings and can therefore create a misleading timeline. Another big problem is that the distribution of time can change significantly if the actual recursive PARSE, EXEC and FETCH is just lumped in to the parent statement’s recursive depth zero parse time rather than being categorized through each recursive level. A more accurate picture can be obtained by summarizing all recursive and non-recursive time for each time interval. I believe that this is an accurate representation of time from the standpoint of the entire trace file timeline, but can create some thorny issues for those trying to categorize time at the statement level. At the statement level we get into the issues that were mentioned in Part 1 of my Trace Event Timeline series.
To implement this new accuracy level requires that for each recursive level that we track the PARSE, EXEC and FETCH time of each statement’s recursive children along with that statement’s exclusive time, and then track that based on the interval time. This then provides the current totals for each time category as each statement, or wait event for that matter, is emitted. Since interval boundaries are checked as each trace file statement is encountered, when a boundary is crossed we now have an accounting of the current cpu time regardless of recursive depth. I will post a comparison of the trace event timeline that I first proposed and this new method of categorizing all recursive time shortly.
Entries