Exporting Multiple Tables on a Common Filter

To be frank, I consider myself novice when it comes to advanced export/import requirements. This is because I don’t deal with these utilities on a day-to-day basis.

A simple requirement came across my desk to export selected tables from a schema based on a common filter.

Requirement:

Say, you have 5 tables T1, T2, T3, T4, and T5. All have “ID” as the primary key column and you have to export data from these tables only if it is found in COMMON_TABLE. The COMMON_TABLE stores “ID” to be exported.

Solution:

The first place that I look for solution is “Oracle Documentation”. I knew we can filter a table using “QUERY” parameter of Data Pump Export but did not know how to apply it on multiple tables.

The syntax of the QUERY parameter is:

QUERY = [schema.][table_name:] query_clause

If you omit [schema.][table_name:] then the query is applied to all the tables in the export job.

So, here’s my export command:

expdp test/test DIRECTORY=data_pump_dir TABLES=t1,t2,t3,t4,t5 DUMPFILE=test.dmp QUERY=\"WHERE id IN \(SELECT common_table.id FROM common_table\)\"

You may click here to read more about the QUERY parameter of Data Pump Export.

Thanks for reading!!!

RACcheck for Single Instance Databases

Starting with RACcheck 2.2.0, RACcheck support is extended to Oracle Single Instance Databases, Oracle Restart and RAC One Node configurations. 


I downloaded the latest version of the tool and tested it against my play database. Below is a sample RACcheck output from a single instance database:

[oracle@localhost raccheck]$ ./raccheck -v

RACCHECK  VERSION: 2.2.0_20121109

[oracle@localhost raccheck]$ 

[oracle@localhost raccheck]$ 

[oracle@localhost raccheck]$ ./raccheck -a

List of running databases

1. testdb

2. None of above

Select databases from list for checking best practices. For multiple databases, select 1 for All or comma separated number like 1,2 etc [1-2][1].

. .

Checking Status of Oracle Software Stack - Clusterware, ASM, RDBMS

. . . . . . . . . . . . . . .

-------------------------------------------------------------------------------------------------------

                                                 Oracle Stack Status                           

-------------------------------------------------------------------------------------------------------

Host Name  CRS Installed  ASM HOME       RDBMS Installed  CRS UP    ASM UP    RDBMS UP  DB Instance Name

-------------------------------------------------------------------------------------------------------

localhost   No              No              Yes             No         No       Yes      testdb  

-------------------------------------------------------------------------------------------------------

Refer to the MOS document mentioned below to learn more about RACcheck tool. You may download the latest version of RACcheck from My Oracle Support (MOS).

References: 

RACcheck - RAC Configuration Audit Tool [ID 1268927.1]

Bug: ORA-00979: not a GROUP BY expression

Bugs and performance degradation are part of database upgrade stories and we have witnessed yet another post-upgrade bug after upgrading our database from Oracle 10gR2 (10.2.0.5) to Oracle 11gR2 (11.2.0.2). 

Following query (I have simplified the query for the demonstration purpose) was running happily within Oracle 10gR2:


SQL>
SQL> select * from ( select TRUNC(dt,'MM')
  2          from test
  3          group by TRUNC(dt,'mm'));

TRUNC(DT,
---------
01-JAN-13

SQL>


However, the same query started to throws an error (ORA-00979) when executed in Oracle 11gR2 (11.2.0.2): 


SQL> select * from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE    11.2.0.2.0      Production
TNS for Linux: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production

SQL> 


SQL> select * from ( select TRUNC(dt,'MM')
          from test
          group by TRUNC(dt,'mm'));
  2    3  select * from ( select TRUNC(dt,'MM')
                             *
ERROR at line 1:
ORA-00979: not a GROUP BY expression


SQL> 

At this point I normally do a search on My Oracle Support (MOS) to see if I get  some hits pertaining to this problem and found the following bug information:

Bug 11067251 - False ORA-979 with TRUNC(date, format) or ROUND(date, format) - superceded [ID 11067251.8]


Apparently, you hit the bug when you use either TRUNC or ROUND functions in an inline view. Executing the same query with little modification (removing inline view) in 11.2.0.2 was however successful.


SQL> select TRUNC(dt,'MM')
 from test
group by TRUNC(dt,'mm');
  2    3  
TRUNC(DT,
---------
01-JAN-13

SQL> 

The above bug confirms that 11.2.0.2 is affected and proposes following two workarounds: 

1) Use NO_MERGE hint or
2) Disable view merging "_simple_view_merging=false" 

As it was not possible to rewrite the application at this point, so we disabled view merging at the system level. Well, disabling view merging at the system level might appear as a bad choice but I think it is a right decision at this time. We will soon be upgrading this database to 11.2.0.3. This will kill two birds with one stone, a) bug fix and b) upgrading to the latest patch level (who knows what new bugs are waiting for us ???).

References: 

• My Oracle Support:  Bug 11067251 - False ORA-979 with TRUNC(date, format) or ROUND(date, format) - superceded [ID 11067251.8]