Oracle Virtualization and Cloud Consulting
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The impact of ASSM on Clustering of data

Automatic Segment Space Management ("ASSM") is designed to reduce block-level contention by multiple sessions concurrently attempting INSERTs by using a bitmap to identify blocks that are on the FreeList. The FreeList is accessed by sessions attempting to insert a row in a table when they need to identify "candidate" blocks. In Manual Segment Space Management ("MSSM"), it is the block-level storage parameter PCTUSED that is a determinant for when a block "enters" and "exits" the freelist.

Controlfiles : Number and Size

A forums thread "Maximum number of Control Files" allowed me to express my opinions about why, for very practical reasons, Oracle does not allow very many multiplexed copies of the controlfile and why the controlfile is "limited" in size.

Here are my two responses :
On the "maximum number of control files" :

You have to consider how Oracle uses the control file.

RMAN Tips -- 3

ALWAYS mention the actual Start and End Times and Contents of all backups.

Whenever you
a. Post a query on forums / email lists
b. Talk to a colleague
c. Report to your manager
*always* mention the Start and End times and contents of your backups.
"Weekly Full Backup and Daily Incremental Backup" is empty of meaning when attempting to resolve a Backup-Restore issue.

Another example of GATHER_TABLE_STATS and a Histogram

In response to a forum thread "Why not selecting index path .", I ran up this example :

SQL> select banner from v$version where rownum=1;

Oracle Database 11g Enterprise Edition Release - Production

SQL> drop table test_index_count5 purge;

Table dropped.

SQL> alter system flush shared_pool;

System altered.

Oracle Android App

Yesterday, I downloaded and installed the Oracle Android App onto my Samsung Galaxy S phone.
I must say : the App provides a quick overview of what's happening in the Oracle World.
It is certainly much faster and better organised than the FaceBook App.
It provides listings of news updates and a few blog posts.


An Index that is a "subset" of a pre-existing Index

It is a common [mis]understanding that creating a new Index that is a subset of an existing Index is an unnecessary overhead. The argument goes "if you have an Index on (A,B,C) this Index can be used to satisfy queries where predicate 'A' is specified, so creating an additional Index on (A) alone is an unnecessary overhead".

Oracle Database Architect Position at SCB

See Oracle Database Architect Position at SCB

DO NOT send me your emails / resumes. Please follow the instructions given in the advertisement.

RMAN Tips -- 2

Incremental Backup from a particular SCN

RMAN allows you to take an Incremental Backup "FROM SCN". Why ? For the purpose of updating a Standby Database.

[oracle@localhost ~]$ sqlplus '/ as sysdba'

SQL*Plus: Release Production on Tue Sep 20 23:35:38 2011

Copyright (c) 1982, 2009, Oracle. All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

Very successful Golden Gate workshop at SG RACSIG

Jigar led the Singapore RACSIG Golden Gate workshop very well today. It was quite apparent that he knows the product well and is enthusiastic about sharing his knowledge.
Ravi also added a few observations and asked "review questions" of the members present.

Thank you very much Jigar.
Thank you Ravi.


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