On a Single-Instance Oracle Database, Application Services offer benefits for Performance Monitoring & Tracing. That’s the focus of this posting. If you are on RAC respectively Data Guard already, you will use Services at least to provide Connect-Time Failover. You may find some additional useful things to do with them here. The playing field:

SQL> select * from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
PL/SQL Release 11.2.0.3.0 - Production
CORE    11.2.0.3.0    Production
TNS for Linux: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production

My demo DB has no Application Services yet. In the most simple case, there is one Application running and we take backups, so that gives us two services to introduce:

SQL> exec dbms_service.create_service('app1','app1')

PL/SQL procedure successfully completed.

SQL> exec dbms_service.create_service('bk','bk')

PL/SQL procedure successfully completed.

With Grid Infrastructure installed, we would use srvctl add service instead. The services are not yet started. Subsequently, an after startup on database trigger should do that.

SQL> exec dbms_service.start_service('app1')

PL/SQL procedure successfully completed.

SQL> exec dbms_service.start_service('bk')

PL/SQL procedure successfully completed.

SQL> grant dba to adam identified by adam;

Grant succeeded.

SQL> exec dbms_workload_repository.create_snapshot

PL/SQL procedure successfully completed.

SQL> select snap_id,to_char(begin_interval_time,'yyyy-mm-dd:hh24:mi:ss') 
from dba_hist_snapshot order by 1;  

   SNAP_ID TO_CHAR(BEGIN_INTER
---------- -------------------
     2 2012-01-18:15:09:15
     3 2012-01-18:15:20:30
     4 2012-01-19:12:51:40
     5 2012-03-19:12:03:03
     6 2012-10-31:14:59:25

The following uses Easy Connect (my host is named uhesse1; my Listener Port is 1521) to attach to the services:

SQL> connect adam/adam@uhesse1/app1
Connected.
SQL> alter session set workarea_size_policy=manual;

Session altered.

SQL> alter session set sort_area_size=100000000;

Session altered.

SQL> create table sales as select 
rownum as id,
mod(rownum,5) as channel_id,
mod(rownum,1000) as cust_id,
5000 as amount_sold,
sysdate as time_id
from dual connect by level<=1e6;    

Table created.

SQL> update sales set amount_sold=amount_sold*1;

1000000 rows updated.

SQL> commit;

Commit complete.

SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
[oracle@uhesse1 ~]$ rman target sys/oracle@uhesse1/bk

Recovery Manager: Release 11.2.0.3.0 - Production on Wed Oct 31 15:13:04 2012

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

connected to target database: PRIMA (DBID=2003897072)

RMAN> backup database;

Starting backup at 31-OCT-12
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=50 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00001 name=/home/oracle/prima/system01.dbf
input datafile file number=00002 name=/home/oracle/prima/sysaux01.dbf
input datafile file number=00003 name=/home/oracle/prima/undotbs01.dbf
input datafile file number=00004 name=/home/oracle/prima/users01.dbf
channel ORA_DISK_1: starting piece 1 at 31-OCT-12
channel ORA_DISK_1: finished piece 1 at 31-OCT-12
piece handle=/home/oracle/flashback/PRIMA/backupset/2012_10_31/o1_mf_nnndf_TAG20121031T151314_892dhwso_.bkp tag=TAG20121031T151314 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:15
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
including current SPFILE in backup set
channel ORA_DISK_1: starting piece 1 at 31-OCT-12
channel ORA_DISK_1: finished piece 1 at 31-OCT-12
piece handle=/home/oracle/flashback/PRIMA/backupset/2012_10_31/o1_mf_ncsnf_TAG20121031T151314_892djcbb_.bkp tag=TAG20121031T151314 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 31-OCT-12

RMAN> exit

Recovery Manager complete.
[oracle@uhesse1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Wed Oct 31 15:13:41 2012

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

SQL> exec dbms_workload_repository.create_snapshot

PL/SQL procedure successfully completed.

SQL> select snap_id,to_char(begin_interval_time,'yyyy-mm-dd:hh24:mi:ss') 
from dba_hist_snapshot order by 1;   

   SNAP_ID TO_CHAR(BEGIN_INTER
---------- -------------------
     2 2012-01-18:15:09:15
     3 2012-01-18:15:20:30
     4 2012-01-19:12:51:40
     5 2012-03-19:12:03:03
     6 2012-10-31:14:59:25
     7 2012-10-31:15:06:13

6 rows selected.

Some „Application“ load was followed by an RMAN backup. We can now differentiate those loads. The AWR report for the last two snapshots show this section:

We can tell from the low values of DB Time for the bk service in relation to the app1 service that the (Online-)Backup has had almost no impact on performance for end users here. Also, we have v$-views for services:

SQL> set lines 200
set pages 300
col service_name for a10
select service_name,event,time_waited 
from v$service_event natural join v$event_name 
where service_name in ('app1','bk') 
and wait_class<>'Idle' 
order by 1,3; 

SERVICE_NA EVENT                                                            TIME_WAITED
---------- ---------------------------------------------------------------- -----------
app1       control file sequential read                                               0
app1       SQL*Net message to client                                                  0
app1       db file single write                                                       1
app1       db file scattered read                                                     1
app1       log file sync                                                              1
app1       control file parallel write                                                1
app1       direct path write                                                          2
app1       direct path sync                                                           3
app1       Data file init write                                                       3
app1       Disk file operations I/O                                                   4
app1       buffer busy waits                                                          5
app1       free buffer waits                                                         13
app1       log file switch (private strand flush incomplete)                         14
app1       db file sequential read                                                   26
app1       log file switch completion                                                28
app1       log buffer space                                                        1635
bk       Parameter File I/O                                                           0
bk       db file scattered read                                                       0
bk       SQL*Net message to client                                                    0
bk       SQL*Net break/reset to client                                                0
bk       db file single write                                                         0
bk       db file sequential read                                                      2
bk       control file parallel write                                                  7
bk       control file single write                                                    8
bk       Disk file operations I/O                                                    12
bk       control file sequential read                                                18
bk       events in waitclass Other                                                  217
bk       RMAN backup & recovery I/O                                                 757

28 rows selected.

SQL> select service_name,value 
from v$service_stats 
where service_name in ('app1','bk') 
and stat_name='physical reads';    

SERVICE_NA    VALUE
---------- ----------
app1            13422
bk                351

There are completely different Top Wait-Events for the two services. ‚physical reads‘ was just one example from the hundreds of available stats. In the very same manner, multiple applications running on the same DB could be differentiated. Furthermore, we can switch on tracing now for only certain services resp. applications:

SQL> exec dbms_monitor.serv_mod_act_trace_enable('app1')

PL/SQL procedure successfully completed.

SQL> connect adam/adam@uhesse1/app1
Connected.
SQL> select count(*) from sales;

  COUNT(*)
----------
   1000000

SQL> select distinct channel_id from sales;

CHANNEL_ID
----------
     1
     2
     4
     3
     0

SQL> connect / as sysdba
Connected.
SQL> exec dbms_monitor.serv_mod_act_trace_disable('app1')

PL/SQL procedure successfully completed.

This kind of service tracing produces potentially many trace files that we can consolidate (and identify) with trcsess like this:

[oracle@uhesse1 trace]$ trcsess output=app1.trc service=app1 *.trc

Afterwards, we can get a better readable output of the trace file with tkprof as usual, showing all the statements of the applications together with their execution plans.

Conclusion: You will always implement Application Services with RAC respectively Data Guard. For Single-Instance, you should use them also because

1) You may use RAC resp. Data Guard in the future and then you have everything in place already

2) You can do Performance Monitoring with a finer granule (on the Application layer) with them

3) You can trace with a finer granule as well