Intro
I recently had a situation where I was troubleshooting a system that had fallen victim to some intermittent and very high load averages. At first, there were no apparent reasons for the high load averages, so that sent me searching for some monitoring tools to help identify the issue. Besides using OSWBB and dstat, I also used the oratop utility which turns out to be a great way to get a quick overview and monitor active sessions in near real time in Oracle 11g and 12c databases. It is also RAC and ASM aware.
References
Here’s the MOS note for more info and downloads.
oratop – Utility for Near Real-time Monitoring of Databases, RAC and Single Instance (Doc ID 1500864.1)
Supported Oracle Releases
11gR2 (11.2.0.3, 11.2.0.4)
12cR1
oratop in Action
There is a user guide available for download on the MOS note, but I will show my favorite options.
Startup
> ./oratop -f -d -i 10 / as sysdba
The switches:
f – detailed format option
d – real time wait events ( the default is cumulative )
i – update interval in seconds
The remaining part of the string is the login. Basically, any string that you use for sqlplus should work with oratop.
Output Sections
Here’s an explanation of the sections. These menus can be found when pressing “h” when running oratop in interactive mode.
1 Database
Section 1 - database
Global Database information
Version : Oracle major version
role : database_role
db name : db_unique_name
time [s]: time as of the most recent stats (hh24:mi:ss)
up [T]: database uptime
ins [N]: total number of instance(s)
sn [c,N]: total user sessions (active/inactive)
us [c,N]: number of distinct users
mt [s,N]: global database memory total (sga+pga)
fra [N]: flashback recovery area %used, (red > 90%)
er [N]: diag active problem count (faults)
% db [s,N]: database time as %(dbtime/cpu) (red if > 99%)
2 Instance
Section 2 - instance
Top 5 Instance(s) Activity
o Ordered by Database time desc
ID [c,N]: inst_id (instance id)
%CPU [m,N]: host cpu busy %(busy/busy+idle). (red if > 90%)
LOAD [m,N]: current os load. (red if > 2*#cpu & high cpu)
%DCU [m,N]: db cpu otusef as %host cpu. (red if > 99% & high AAS)
AAS [s,N]: Average Active Sessions. (red if > #cpu)
ASC [c,N]: active Sessions on CPU
ASI [c,N]: active Sessions waiting on user I/O
ASW [c,N]: active Sessions Waiting, non-ASI (red if > ASC+ASI)
ASP [m,N]: active parallel sessions (F/G)
AST [c,N]: Active user Sessions Total (ASC+ASI+ASW)
UST [c,N]: user Sessions Total (ACT/INA)
MBPS [m,N]: i/o megabytes per second (throughput)
IOPS [m,N]: i/o requests per second
IORL [m,T]: avg synchronous single-block read latency. (red > 20ms)
LOGR [s,N]: logical reads per sec
PHYR [s,N]: physical reads per sec)
PHYW [s,N]: physical writes per sec
%FR [s,N]: shared pool free %
PGA [s,N]: total pga allocated
TEMP [s,N]: temp space used
UTPS [s,N]: user transactions per sec
UCPS [c,m,N]: user calls per sec
SSRT [c,m,T]: sql service response time (T/call)
DCTR [m,N]: database cpu time ratio
DWTR [m,N]: database wait time ratio. (red if > 50 & high ASW)
%DBT [s,N]: instance %Database Time (e.g. non-rac shows 100%)
3 Wait Events
Section 3 - db wait events
Top 5 Timed Events
o Cluster-wide, non-idle
o Ordered by wait time desc
EVENT : wait event name. (red if active)
(RT) : Real-Time mode
WAITS : total waits
TIME(s) : total wait time in seconds)
AVG_MS : average wait time in milliseconds
PCT : percent of wait time (all events)
WAIT_CLASS : name of the wait class
4 Processes
Section 4 - process
o Non-Idle processes
o Ordered by event wait time desc
ID [N]: inst_id. (red if blocking)
SID [N]: session identifier. (red if blocking)
SPID [N]: server process os id
USERNAME : Oracle user name
PROGRAM : process program name
SRV : SERVER (dedicated, shared, etc.)
SERVICE : db service_name
PGA [N]: pga_used_mem. (red if continuously growing)
SQL_ID/BLOCKER : sql_id or the final blocker's (inst:sid, in red)
OPN : operation name, e.g. select
E/T [T]: session elapsed time (active/inactive)
STA : ACTive|INActive|KILled|CAChed|SNIped
STE : process state, e.g. on CPU or user I/O or WAIting
WAIT_CLASS : wait_class for the named event
EVENT/*LATCH : session wait event name. Auto toggle with *latch name.
(red if process is hung/spin)
W/T [T]: event wait time. (red if > 1s)
Blocking Sessions
If there are blocking sessions present, the instance and sid will be shown in the SQL ID/BLOCKER column.
Stopping
To quit the program, user may press any of the following keyboard keys:
Character “q” or “Q”, or Esc key
Ctrl+c (to abort).
Execution Plans
By pressing “x”, and then giving the sqlid, the explain plan of the sql in question will be displayed. Although this is a nice and quick feature, it does not show as much detail about the plan as the display_cursor procedure will as shown below. As far as I can tell, it does show the actual plan and not the estimated ones that are displayed without acttually running the query, but I have not thorougly tested this.
select * from table(dbms_xplan.display_cursor(‘&sql_id’,’&child_no’,’typical’));
Space
The “a” option can be used to show info on the disk groups.
The “t” option can be used to show info on the tablespaces.
