Kumar,The SCAN listeners don't have an effect on TAF except it's easier to write tnsnames.ora files.
Let's have an example-3 node RAC 11.2.0.2 on Linux, database orcl, service oraclel, TAF configuration in tnsnames.ora. Creating the new service:
[oracle@rac11gr2drnode1 ~]$ srvctl add service -d orcl -r orcl1 -a orcl2 -s oraclel
[oracle@rac11gr2drnode1 ~]$ srvctl start service -d orcl -s oraclel It has only 1 preferred instance: [oracle@rac11gr2drnode1 ~]$ srvctl config service -d orcl -s oraclel Service name: oraclel Service is enabled Server pool: orcl_oraclel Cardinality: 1 Disconnect: false Service role: PRIMARY Management policy: AUTOMATIC DTP transaction: false AQ HA notifications: false Failover type: NONE Failover method: NONE TAF failover retries: 0 TAF failover delay: 0 Connection Load Balancing Goal: LONG Runtime Load Balancing Goal: NONE TAF policy specification: NONE Edition: Preferred instances: orcl1 Available instances: orcl2 local TNSNames.ora: ORACLEL = (DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST = drclusterscan.localdomain)(PORT = 1521))
(CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = oraclel) (failover_mode = basic)(failover_type = session) ) ) Connect to the database: sqlplus martin@oraclel SQL> select inst_id,sid,serial#,FAILOVER_TYPE, failover_method, failed_over 2 from gv$session where sid=(select distinct sid from v$mystat) 3 / INST_ID SID SERIAL# FAILOVER_TYPE FAILOVER_M FAI ---------- ---------- ---------- ------------- ---------- --- 1 33 393 SESSION BASIC NO SQL> r 1* select * from v$active_instances INST_NUMBER INST_NAME ----------- ------------------------------------------------------------ 1 rac11gr2drnode1.localdomain:orcl1 2 rac11gr2drnode3.localdomain:orcl2 3 rac11gr2drnode4.localdomain:orcl3 Let's kill the instance: [oracle@rac11gr2drnode1 ~]$ srvctl stop instance -d orcl -i orcl1 -o abort [oracle@rac11gr2drnode1 ~]$ srvctl status database -d orcl Instance orcl1 is not running on node rac11gr2drnode1 Instance orcl2 is running on node rac11gr2drnode3 Instance orcl3 is running on node rac11gr2drnode4 what happened to the session? SQL> r 1* select * from v$active_instances select * from v$active_instances * ERROR at line 1: ORA-03113: end-of-file on communication channel Process ID: 9770 Session ID: 33 Serial number: 393 You /will/ lose your session with only 1 preferred instance and TAF. Let's change the service to have 2 preferred instances:[oracle@rac11gr2drnode1 oracle-l]$ srvctl modify service -d orcl -s oraclel -n -i orcl1,orcl2 -a orcl3
[oracle@rac11gr2drnode1 oracle-l]$ srvctl config service -d orcl -s oraclel Service name: oraclel Service is enabled Server pool: orcl_oraclel Cardinality: 2 Disconnect: false Service role: PRIMARY Management policy: AUTOMATIC DTP transaction: false AQ HA notifications: false Failover type: NONE Failover method: NONE TAF failover retries: 0 TAF failover delay: 0 Connection Load Balancing Goal: LONG Runtime Load Balancing Goal: NONE TAF policy specification: NONE Edition: Preferred instances: orcl1,orcl2 Available instances: orcl3 [oracle@rac11gr2drnode1 oracle-l]$ srvctl start service -d orcl -s oraclel [oracle@rac11gr2drnode1 oracle-l]$ srvctl status service -d orcl -s oraclel Service oraclel is running on instance(s) orcl1,orcl2 we now have 2 preferred instances. Let's retry the test: SQL> select inst_id,sid,serial#,FAILOVER_TYPE, failover_method, failed_over 2 from gv$session where sid=(select distinct sid from v$mystat) 3 and inst_id = sys_context('userenv','instance') 4 / INST_ID SID SERIAL# FAILOVER_TYPE FAILOVER_M FAI ---------- ---------- ---------- ------------- ---------- --- 2 151 23 SESSION BASIC NO [oracle@rac11gr2drnode1 ~]$ srvctl stop instance -d orcl -i orcl2 -o abort [oracle@rac11gr2drnode1 ~]$ srvctl status database -d orcl Instance orcl1 is running on node rac11gr2drnode1 Instance orcl2 is not running on node rac11gr2drnode3 Instance orcl3 is running on node rac11gr2drnode4 back to my session: SQL> / select inst_id,sid,serial#,FAILOVER_TYPE, failover_method, failed_over * ERROR at line 1: ORA-25408: can not safely replay call SQL> / INST_ID SID SERIAL# FAILOVER_TYPE FAILOVER_M FAI ---------- ---------- ---------- ------------- ---------- --- 1 153 11 SESSION BASIC YESDon't know why the ORA-25408 appears, I didn't ask for read consistent failover. In your application you have to catch the 25408 in a SQLException or you will be bailed out anyway.
Hope this helps, Martin http://uk.linkedin.com/in/martincarstenbach http://martincarstenbach.wordpress.com <http://uk.linkedin.com/in/martincarstenbach> On 16/08/2011 14:12, Kumar Madduri wrote:
Hi MartinWith the introduction of SCAN listeners, this behavior should not happen or it should have minimum impact. Is this right?Thank you KumarOn Tue, Aug 16, 2011 at 3:52 AM, Martin Bach <development@xxxxxxxxxxxxxxxxx <mailto:development@xxxxxxxxxxxxxxxxx>> wrote:Hi Jed, indeed, the service will fail over in case your preferred instance crashes. However, your sessions won't-it's quite simple to test. Define TAF at the service level, define 1 preferred and n (where n > 0) available instances, start the service, connect to the service and then kill the instance. You can do this in SQLPlus, and you'll see that your connection lost contact. Does that quick reply make sense? I don't have a system available right now, but can do a test if you like and share the output. Best regards, Martin On 15/08/2011 16:04, Walker, Jed S wrote:Thank you Martin, Frits, Toon, and Kumar. Question though, If I have a service with one preferred instance and multiple available instances I believe it should still failover with TAF to any of the available instances shouldn’t it? My understanding is that multiple preferred instances is for spreading the load across multiple instances, not failover. *From:*Martin Bach [mailto:development@xxxxxxxxxxxxxxxxx] *Sent:* Saturday, August 06, 2011 7:33 AM *To:* Frits Hoogland; toon.koppelaars@xxxxxxxxxxx <mailto:toon.koppelaars@xxxxxxxxxxx> *Cc:* Walker, Jed S; oracle-l@xxxxxxxxxxxxx <mailto:oracle-l@xxxxxxxxxxxxx> *Subject:* Re: RAC design question Hi, I would like to put one or two more points into the discussion. If you would like to prevent connections from dropping by employing TAF you need at least 2 preferred instances. I also got best results from FCF with the same setup, plus it could give you runtime load balancing. But then again I haven't heard of anyone using FCF (and UCP) in real world applications ... Since you didn't tell us more about your application you need to decide if these points are applicable. If you really only needed higher availability you could have with an active passive cluster and saved on licenses... How this helps, Martin Martin Bach Martin Bach Consulting http://martincarstenbach.wordpress.com <http://martincarstenbach.wordpress.com/> http://www.linkedin.com/in/martincarstenbach ----- Reply message ----- From: "Frits Hoogland" <frits.hoogland@xxxxxxxxx> <mailto:frits.hoogland@xxxxxxxxx> Date: Sat, Aug 6, 2011 08:57 Subject: RAC design question To: "toon.koppelaars@xxxxxxxxxxx" <mailto:toon.koppelaars@xxxxxxxxxxx> <toon.koppelaars@xxxxxxxxxxx> <mailto:toon.koppelaars@xxxxxxxxxxx> Cc: "Jed_Walker@xxxxxxxxxxxxxxxxx" <mailto:Jed_Walker@xxxxxxxxxxxxxxxxx> <Jed_Walker@xxxxxxxxxxxxxxxxx> <mailto:Jed_Walker@xxxxxxxxxxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <mailto:oracle-l@xxxxxxxxxxxxx> <oracle-l@xxxxxxxxxxxxx> <mailto:oracle-l@xxxxxxxxxxxxx> With the clusterware you can setup a service for every schema which can fail over to another instance. Frits Hoogland http://fritshoogland.wordpress.com <http://fritshoogland.wordpress.com/> mailto:frits.hoogland@xxxxxxxxx <frits.hoogland@xxxxxxxxx <mailto:frits.hoogland@xxxxxxxxx>> cell: +31 6 53569942 <tel:%2B31%206%2053569942> Op 6 aug. 2011 om 08:22 heeft Toon Koppelaars <toon.koppelaars@xxxxxxxxxxx <mailto:toon.koppelaars@xxxxxxxxxxx>> het volgende geschreven: I think you've answered that design question very wisely. On Sat, Aug 6, 2011 at 12:49 AM, Walker, Jed S <Jed_Walker@xxxxxxxxxxxxxxxxx <mailto:Jed_Walker@xxxxxxxxxxxxxxxxx%0b>> wrote: > Hi,**** > > ** ** > > I’m new to RAC, but have a question. We have a 5 node RAC that supports > multiple markets each of which has its own schema. Due to each market having > its own schema, there is no sharing of blocks between markets. As such, I am > thinking that it would make sense to have each market work on only one node > because that would avoid having blocks passed between nodes, and thus should > be good for performance. (Note: the intent behind RAC was for high > availability, not for scaling, each node can handle the workload of multiple > markets).**** > > ** ** > > Thoughts?**** > > ** ** > > **- **Jed**** > > ** ** >-- Toon KoppelaarsRuleGen BV Toon.Koppelaars@xxxxxxxxxxx <mailto:Toon.Koppelaars@xxxxxxxxxxx> www.RuleGen.com <http://www.rulegen.com/> TheHelsinkiDeclaration.blogspot.com <http://thehelsinkideclaration.blogspot.com/> (co)Author: "Applied Mathematics for Database Professionals" www.rulegen.com/am4dp-backcover-text <http://www.rulegen.com/am4dp-backcover-text>