Laurent Schneider

What are my groups?

PS> Get-ADPrincipalGroupMembership lsc |
      select -ExpandProperty "name"
Domain Users
oracle
sybase

PS> Get-ADGroupMember oracle| 
      select -ExpandProperty "name"
Laurent Schneider
Alfred E. Newmann
Scott Tiger

PS> (get-aduser lsc -property MobilePhone).MobilePhone
+41 792134020

This works like a charm on your Windows 7 PC.
1) Download and install Remote Server Administration Tools
2) Activate the windows feature under control panel program called “Active Directory Module for Powershell”
3) PS> Import-Module ActiveDirectory
Read the procedure there : how to add active directory module in powershell in windows 7

Oracle 12cR1 patchset 1 is due this month and there is a new parameter that you can set to boost your performance. It is a bit of a SET "_FAST"=true parameter.

The in memory parameter is part of the sga. It is not mandatory to size it correctly, even if you do not have enough memory to hold your complete database, you can still play around with this parameter.

In a way, alter table t inmemory reminds me to the Oracle 8i alter table t cache and the Oracle 9i alter table t storage (buffer_pool keep).

But it is not free, I expect something close to the partitioning option, and it surely requires Enterprise Edition.

And also Oracle makes big noise about it, experts talk about a 1000x improvement, watch Database Industry Experts Discuss Oracle Database In-Memory.

The in memory cache is redundant with the database cache. It stores columns instead of blocks (or even results with the RESULT CACHE in 11g)

Don’t miss the Oracle Blog of @db_inmemory

Providing in-memory database is also positioning against HANA, a SAP in memory database. From OTN : Oracle Database In-Memory
Versus SAP HANA

A few years ago, Oracle acquired TimesTen. TimesTen is an in-memory database that works differently, where you can have fast response time (microseconds?) and could lose transactions (better faster than zero-data-loss). While TimesTen improves transaction speed, inMemory mostly improves queries (not writes).

There are 2 versions to check when using jdbc.

The first one is in the name of the file : classes12.zip works with JDK 1.2 and later, ojdbc7.jar works with java7 and later.

Even if classes12.zip works fine with JAVA 8, it is not supported.

Be sure you check the support matrix on the Oracle JDBC FAQ

According to the support note 401934.1, only Oracle JDBC driver 11.2.0.3 (and greater) versions support JDK 1.7.

To check your version of the JDBC Driver, there are two methods.

One is with the jar (or zip) utility.

$ jar -xvf ojdbc7.jar META-INF/MANIFEST.MF
 inflated: META-INF/MANIFEST.MF
$ grep Implementation META-INF/MANIFEST.MF
Implementation-Vendor: Oracle Corporation
Implementation-Title: JDBC
Implementation-Version: 12.1.0.1.0
$ unzip classes12.zip META-INF/MANIFEST.MF
Archive:  classes12.zip
  inflating: META-INF/MANIFEST.MF
$ grep Implementation META-INF/MANIFEST.MF
Implementation-Title:   classes12.jar
Implementation-Version: Oracle JDBC Driver 
  version - "10.2.0.1.0"
Implementation-Vendor:  Oracle Corporation
Implementation-Time:  Jun 22 18:51:56 2005

The last digit is often related to the java version, so if you have ojdbc6 and use java 6, you’re pretty safe. If you have java 8, you won’t find any ojdbc8 available at the time of writing, a safer bet is to use the latest version and to wait for a support note. The latest notes about ojdbc7.jar currently does not display java 8 certification. Probably we will have to wait for a more recent version of ojdbc7.jar.

Another mean to find the version of the driver is to use DatabaseMetaData.getDriverVersion()

public class Metadata {
  public static void main(String argv[]) 
    throws java.sql.SQLException {
    java.sql.DriverManager.registerDriver(
      new oracle.jdbc.driver.OracleDriver());
    System.out.println(
      java.sql.DriverManager.
        getConnection(
"jdbc:oracle:thin:@SRV01.EXAMPLE.COM:1521:DB01", 
          "scott", "tiger").
            getMetaData().getDriverVersion());
  }
}

$ javac -classpath ojdbc6.jar Metadata.java
$ java -classpath ojdbc6.jar:. Metadata
11.2.0.3.0

Today I find out that my scheduler was too busy to execute all jobs in my crontab !?

* * * * * (while :;do ssh example.com :; done)
59 23 19 06 * touch /tmp/bang

my while loop is going to produce so much hangs on the cron deamon that it may not be able to read the crontab once a minute. If it reads it at 23:58 and at 00:00, the 23:59 won’t be run.

This is actually the first time I see this behaviour. And -believe me- it’s annoying!

One limitation in listagg, you cannot use DISTINCT. Okay, there are plenty of distinct-capable listagg workarounds, but to get the real listagg working, it is a bit of an headache

With one listagg

SELECT 
  DEPTNO,
  LISTAGG (JOB, ',') 
    WITHIN GROUP (ORDER BY JOB) JOBS
FROM (
  SELECT DISTINCT DEPTNO, JOB  FROM EMP)
GROUP BY DEPTNO;

    DEPTNO JOBS                          
---------- ------------------------------
        10 CLERK,MANAGER,PRESIDENT       
        20 ANALYST,CLERK,MANAGER         
        30 CLERK,MANAGER,SALESMAN        

ok, it was not that hard, but it gets more difficult with two listagg’s

SELECT 
  LISTAGG (job, ',') 
    WITHIN GROUP (ORDER BY job) jobs,
  LISTAGG (deptno, ',') 
    WITHIN GROUP (ORDER BY deptno) deptnos
FROM (
  SELECT 
    DECODE(
      ROW_NUMBER () OVER (
        PARTITION BY deptno 
        ORDER BY 1),
      1, deptno) deptno,
    DECODE (
      ROW_NUMBER () OVER (
        PARTITION BY job 
        ORDER BY 1),
      1, job) job
  FROM emp
);
DEPTNOS  JOBS                                      
-------- ----------------------------------------
10,20,30 ANALYST,CLERK,MANAGER,PRESIDENT,SALESMAN

Too bad the DISTINCT keyword was not implemented

There is an obscure syntax that prevents a procedure from issuing a commit

alter session DISABLE COMMIT IN PROCEDURE;

According to the doc, it prevents procedure from committing your data

Test case

SQL> alter session DISABLE COMMIT IN PROCEDURE
Session altered.
SQL> create table t(x number)
Table created.
SQL> create or replace procedure p is 
begin
  commit;
end;
Procedure created.
SQL> insert into t values (1)
1 row created.
SQL> exec p
BEGIN p; END;
Error at line 17
ORA-00034: cannot COMMIT in current PL/SQL session
ORA-06512: at "SCOTT.P", line 3
ORA-06512: at line 1

But some sys procedures may bypass this restriction

SQL> exec dbms_stats.gather_table_stats(user, 'T')
 PL/SQL procedure successfully completed.
SQL> rollback
Rollback complete.
SQL> select * from t

         X
----------
         1

The row was silently committed.