Database link failover on RAC

Dear Friends.
Could you please provide me the information about implementation of Database links failover in RAC. (Oracle 10g RAC on linux)
I have created db links across the two RAC environments. Each RAC setup contains 2 nodes.
I have created DB link across the two RAC environemtns.
i.e I have created DB link between 1st node of Source RAC system to 1st node of Target RAC system.
If 1st node of Target RAC system is down, I need to setup in such way that the link should failover to node 2 of Target system.
I have tried all possible options of TAF. But I did not succeed. Is there anybody is implemented this type setup...?
How to setup tnsnames.ora on source DB to get this type of failover.
Thanks in Advance.
Best Regards
Kanumuri Raju

Oracle was kind enough to provide some configuration details in their docco. You may want to review this link:
http://download-east.oracle.com/docs/cd/B19306_01/network.102/b14212/advcfg.htm#sthref1275
The configuration needs to be performed in the TNSNAMES.ORA associated with the database initiating the link. If you want bi-directional TAF, you would need to update the TNSNAMES.ORA for 'both' databases.
I suggest you don't get your hopes up too high about the capability of TAF across DBLinks. I'm pretty sure you will not be able to get SELECT-based TAF. And I'm not absolutely sure which session rules will be used to determine the failover time.

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I have a database that uses a dblink to connect to a remote database to use a sequence for id's. The remote database is a 12 node rac cluster and when the database link was initially created the admin that created it only specified one of the nodes in the rac cluster in the comnnection description for the database link.
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2 for not_a_user.not_a_table@not_a_link;
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SQL> select status from dba_objects where object_name = 'INVALID_SYNONYM';
STATUS
VALIDYou'll get an error if you try to use the synonym, of course, but it won't be invalid. As long as you fix the database link before someone tries to use the synonym, there is no issue.
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Probando...
Fallo.
SQL Exception
Error del repositorio: Excepción SQL.
Nombre de la Clase: CacheMediator.
Nombre del Método: getDDEntryFromDB.
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userid scott
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So, here's my simple test.
SQL>
SQL> create table gurnish.indexes20plus ( n1 number, n2 number, n3 number, n4 number, n5 number, n6 number, n7 number,
2 n8 number, n9 number, n10 number, n11 number, n12 number, n13 number, n14 number, n15 number, n16 number,
3 n17 number, n18 number, n19 number, n20 number, n21 number, n22 number, n23 number, n24 number,
4 n25 number, n26 number, n28 number);
create index xin1 on indexes20plus (n1);
Table created.
SQL> SQL> create index xin2 on indexes20plus (n2);
create index xin3 on indexes20plus (n3);
Index created.
SQL> SQL>
Index created.
SQL> SQL> create index xin4 on indexes20plus (n4);
Index created.
SQL> SQL>
Index created.
SQL> SQL> create index xin5 on indexes20plus (n5);
create index xin6 on indexes20plus (n6);
Index created.
SQL> SQL>
Index created.
SQL> SQL> create index xin7 on indexes20plus (n7);
Index created.
SQL> SQL> create index xin8 on indexes20plus (n8);
Index created.
SQL> SQL> create index xin9 on indexes20plus (n9);
Index created.
SQL>
SQL> create index xin10 on indexes20plus (n10);
Index created.
SQL> SQL> create index xin11 on indexes20plus (n11);
create index xin12 on indexes20plus (n12);
create index xin13 on indexes20plus (n13);
Index created.
SQL> SQL>
Index created.
SQL> SQL>
Index created.
SQL> SQL> create index xin14 on indexes20plus (n14);
Index created.
SQL> SQL> create index xin15 on indexes20plus (n15);
Index created.
SQL>
SQL> create index xin16 on indexes20plus (n16);
Index created.
SQL>
SQL> create index xin17 on indexes20plus (n17);
Index created.
SQL> SQL> create index xin18 on indexes20plus (n18);
Index created.
SQL> SQL> create index xin19 on indexes20plus (n19);
Index created.
SQL> SQL> create index xin20 on indexes20plus (n20);
Index created.
SQL> SQL> create index xin21 on indexes20plus (n21);
Index created.
declare
i number;
begin
for i in 1..100
loop
dbms_random.seed(i+100);
insert into indexes20plus values (dbms_random.value(1,5),dbms_random.value(1,21),dbms_random.RANDOM, dbms_random.RANDOM,dbms_random.value(1,20),
dbms_random.value(1,4),dbms_random.value(1,6), dbms_random.value(1,7),dbms_random.value(1,9),dbms_random.value(1,10),
dbms_random.value(1,11),dbms_random.value(1,12),dbms_random.value(1,13),dbms_random.value(1,14),dbms_random.value(1,1),
dbms_random.value(1,1),dbms_random.value(1,19),dbms_random.value(1,122),dbms_random.value(1,20),dbms_random.value(1,20)
,dbms_random.value(4,20),dbms_random.value(1,20),dbms_random.value(1,20),dbms_random.value(1,20),dbms_random.value(1,20)
,dbms_random.value(4,20),dbms_random.value(4,20));
end loop;
commit;
end;
SQL> set autotrace traceonly
SQL> l
1* select * from gurnish.indexes20plus@lvoprds where n1 = 4
SQL> /
no rows selected
Execution Plan
Plan hash value: 441368878
| Id | Operation | Name | Rows | Bytes | Cost (%CPU
)| Time | Inst |
| 0 | SELECT STATEMENT REMOTE | | 1 | 351 | 1 (0
)| 00:00:01 | |
| 1 | TABLE ACCESS BY INDEX ROWID| INDEXES20PLUS | 1 | 351 | 1 (0
)| 00:00:01 | LVPRD |
|* 2 | INDEX RANGE SCAN | XIN1 | 1 | | 1 (0
)| 00:00:01 | LVPRD |
Predicate Information (identified by operation id):
2 - access("A1"."N1"=4)
Note
- fully remote statement
- dynamic sampling used for this statement
Statistics
0 recursive calls
0 db block gets
0 consistent gets
0 physical reads
0 redo size
1897 bytes sent via SQL*Net to client
481 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
0 rows processed
SQL> select * from gurnish.indexes20plus@lvoprds where n21 = 4;
no rows selected
Execution Plan
Plan hash value: 2929530649
| Id | Operation | Name | Rows | Bytes | Cost (%CPU
)| Time | Inst |
| 0 | SELECT STATEMENT REMOTE | | 1 | 351 | 1 (0
)| 00:00:01 | |
| 1 | TABLE ACCESS BY INDEX ROWID| INDEXES20PLUS | 1 | 351 | 1 (0
)| 00:00:01 | LVPRD |
|* 2 | INDEX RANGE SCAN | XIN21 | 1 | | 1 (0
)| 00:00:01 | LVPRD |
Predicate Information (identified by operation id):
2 - access("A1"."N21"=4)
Note
- fully remote statement
- dynamic sampling used for this statement
Statistics
1 recursive calls
0 db block gets
0 consistent gets
0 physical reads
0 redo size
1897 bytes sent via SQL*Net to client
481 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
0 rows processed
SQL>

HELP! FOR LOOP TO SCROLL THROUGH TABLE AND CREATE DATABASE LINK

Hi,
Here's the scenario, not much of a PL programmer, just basic SQL so really need some help people!
I have 2 tables. 1 contains list of DB's and the other contains rules to follow.
I need to create a loop that goes through the table containing the DB's and on each row a DB link is created (Only 1 link allowed!)
Once created, the schema currently logged in with also has an account on the linked DB in order to run scripts- The scripts are stored centrally hence the requirement for the link to the target DB.
There are numerous scripts that need to be executed and can all be called from 1 script, once executed the loop exists and the database link needs to be dropped.
Once dropped, the first loop continues, creating a DB link for the next DB listed in the table (and all the scripts are fired again)
This continues against all the DB's listed in the table.

Hi BlueShadow,
Thanks again for the response, you've hit the nail on the head. SQL scripts on a unix server, a loop goes through a table 1 at a time. Each row gets a link created and then all the scripts stored on the server are executed against the db linked to. So I'm assuming this is a loop within a loop.
1 loop to go through the table to create the link and then another loop within once connected to execute all the scripts against the connected DB. Once the scripts are run, the loop exits and moves onto the next server and so on until all the servers have the scripts are run.
It's PL/SQL scripts we're after and not shell scripts as this would free us from the OS constraints.
We have to drop the links due to security. Any idea on o

Database link error when compiling forms 6.0 and forms 6i.

Dear sirs,
We have a database link between two databases of the same version oracle 8.0.5.
Recently we have upgraded one of our databases to version 9.2.0.1 (the database where the database link was originally created ) and now we are having problems when compiling forms that have PL/SQL blocks using the database link.
The error message received when compiling the form is the following:
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Is this an ORACLE 9.2.0.1 problem ?
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There is no table in em repository database that contains db link information for database targets. The way to get this info is create a dblink in your em repository database for each database target then create plsql package that connect to each target over dblink and writes the info into a table in em repository table. You could also just create a sql job from em and run against each database target.
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Execute procedure over database link

Hi,
I''m working on a package where you can select the required database, paste some query and with clicking on a button it will execute and create an explain plan for this query.
Therefore i've create a procedure on each database that put's the explain plan in the PLAN_TABLE.
To do this i need to execute this prodecure from the package. I use the following code:
DBA_OWNER.DB_PCD_EXPLAIN_PLAN@DBA_LINK_533.WORLD(p_query);
This is working fine as this database link allready exists to the required database. But i want to make the database link name variable. I've allready created the dynamic database link:
l_link varchar2(20) := 'DBA_LINK';
l_link_nr number(4) := dbms_random.value(0,1000);
l_db varchar2(20) := l_link||'_'||l_link_nr;
l_statement varchar2(4000);
begin
l_statement := 'create database link '||l_db||' connect to **** identified by ***** using '''||p_database||'.WORLD''';
execute immediate l_statement ;
So now i have the dynamic databaselink that is created each time i call the package.
now i want to use this databaselink to call the procedure. this is where it goes wrong.
The code i'm using:
DBA_OWNER.DB_PCD_EXPLAIN_PLAN@l_db(p_query);
is not acceoted when i build the package.
The follwoing error message is showed.
PACKAGE BODY DBA_OWNER.PCK_EXPLAIN_PLAN
On line: 66
PLS-00352: Unable to access another database 'L_DB'
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Any procedures you call have to be accessible at compile time, so the database link must also exist at compile time.
You can get around this by putting your procedure call to DB_PCD_EXPLAIN_PLAN inside dynamic SQL, the same as you are doing to create the database link. Dynamic SQL is not checked until runtime.
Think about the risk if this procedure is exploited. You are creating a way for someone to run arbitrary code in an any database in your environment, with presumably a highly-privileged ID, if it can run an explain plan against any schema in any target database.
This is exposing some significant security issues. Read up on SQL injection, and have someone else review the code for security issues before deploying this.

Interactive report performance problem over database link - Oracle Gateway

Hello all;
This is regarding a thread Interactive report performance problem over database link that was posted by Samo.
The issue that I am facing is when I use Oracle function like (apex_item.check_box) the query slow down by 45 seconds.
query like this: (due to sensitivity issue, I can not disclose real table name)
SELECT apex_item.checkbox(1,b.col3)
, a.col1
, a.col2
FROM table_one a
, table_two b
WHERE a.col3 = 12345
AND a.col4 = 100
AND b.col5 = a.col5
table_one and table_two are remote tables (non-oracle) which are connected using Oracle Gateway.
Now if I run above queries without apex_item.checkbox function the query return or response is less than a second but if I have apex_item.checkbox then the query run more than 30 seconds. I have resolved the issues by creating a collection but it’s not a good practice.
I would like to get ideas from people how to resolve or speed-up the query?
Any idea how to use sub-factoring for the above scenario? Or others method (creating view or materialized view are not an option).
Thank you.
Shaun S.

Hi Shaun
Okay, I have a million questions (could you tell me if both tables are from the same remote source, it looks like they're possibly not?), but let's just try some things first.
By now you should understand the idea of what I termed 'sub-factoring' in a previous post. This is to do with using the WITH blah AS (SELECT... syntax. Now in most circumstances this 'materialises' the results of the inner select statement. This means that we 'get' the results then do something with them afterwards. It's a handy trick when dealing with remote sites as sometimes you want the remote database to do the work. The reason that I ask you to use the MATERIALIZE hint for testing is just to force this, in 99.99% of cases this can be removed later. Using the WITH statement is also handled differently to inline view like SELECT * FROM (SELECT... but the same result can be mimicked with a NO_MERGE hint.
Looking at your case I would be interested to see what the explain plan and results would be for something like the following two statements (sorry - you're going have to check them, it's late!)
WITH a AS
(SELECT /*+ MATERIALIZE */ *
FROM table_one),
b AS
(SELECT /*+ MATERIALIZE */ *
FROM table_two),
sourceqry AS
(SELECT b.col3 x
       , a.col1 y
       , a.col2 z
FROM table_one a
    , table_two b
WHERE a.col3 = 12345
AND   a.col4 = 100
AND   b.col5 = a.col5)
SELECT apex_item.checkbox(1,x), y , z
FROM sourceqry
WITH a AS
(SELECT /*+ MATERIALIZE */ *
FROM table_one),
b AS
(SELECT /*+ MATERIALIZE */ *
FROM table_two)
SELECT apex_item.checkbox(1,x), y , z
FROM table_one a
    , table_two b
WHERE a.col3 = 12345
AND   a.col4 = 100
AND   b.col5 = a.col5If the remote tables are at the same site, then you should have the same results. If they aren't you should get the same results but different to the original query.
We aren't being told the real cardinality of the inners select here so the explain plan is distorted (this is normal for queries on remote and especially non-oracle sites). This hinders tuning normally but I don't think this is your problem at all. How many distinct values do you normally get of the column aliased 'x' and how many rows are normally returned in total? Also how are you testing response times, in APEX, SQL Developer, Toad SQLplus etc?
Sorry for all the questions but it helps to answer the question, if I can.
Cheers
Ben
http://www.munkyben.wordpress.com
Don't forget to mark replies helpful or correct ;)

PL/SQL :ORA-04052 with Database link

i have created a database link in my producation database as following
CREATE PUBLIC DATABASE LINK <NAME>
CONNECT TO <USER>
IDENTIFIED BY <P/W>
USING <CONNECT STRING OF TARGET DATABASE
oracle version 9.0.2.8
OS : Windows 2003 EE R2 SP2
Using oracle failsafe 3.3.4 with windows cluster
Problem Description :
whenever i run my pl/sql procecdure to pull the data from the target database i get the following error
ERROR at line 3
ORA-06550:line 3 column 2
PL/SQL : ORA-04052: error occured when looking up remote object _<SCHEMA>.<TABLE>@<DATABASE LINKE NAME>_
ORA-00604 : ERROR occured at recursive SQL level 1
ORA-03106 : fatal tow-task communication protocol error
ORA-02063: preceding line from <DATABASE LINK NAME>
I have tested the same way in the test environment the same oracle version as well the OS but without oracle failsafe and windows cluster
the script goes smoothly with out any errors.
i have google and checked the OTN for all available solutions but still nothing its not getting throw
i will be very thankful for your replys and solutions
any farther clarification i am ready
thanks in advance

Hi,
This forum is for issues connecting to non-Oracle databases. As the problem is using PL/SQL to connect to another Oracle database then it would be better to post a thread in the PL/SQL forum -
PL/SQL
If you are trying to connect to a non-Oracle database then please give us the details of which non-Oracle database and the software you are trying to use to connect.
Regards,
Mike

Database link failover on RAC

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