Oracle VM Consulting
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Reading an AWR - 1

Given this extract from an AWR :

Instance Efficiency Percentages (Target 100%)
Buffer Nowait %: 100.00 Redo NoWait %: 100.00
Buffer Hit %: 99.93 In-memory Sort %: 100.00
Library Hit %: 94.76 Soft Parse %: 96.21
Execute to Parse %: 30.63 Latch Hit %: 100.00
Parse CPU to Parse Elapsd %: 79.13 % Non-Parse CPU: 93.52

Should I be worried about the Parse ratios ?

Multiple Channels in RMAN are not always balanced

Occasionally, we come across questions about multiple channels and parallelism in RMAN.
Although RMAN distributes the datafiles across the channels, it doesn't necessarily mean that each channel has the same I/O requirements and needs the same amount of time. One channel may be reading more data and writing a larger backup than another.

For example, in this database with 16 datafiles where data is not equally distributed across all the datafiles :

SQL> select file_id, sum(blocks) from dba_extents group by file_id order by 1;

DDL Triggers

A few weeks ago, there was a question about disabling TRUNCATEs. That can be easily done via a Trigger.

But you have to be careful about such triggers. Such a trigger can disable a TRUNCATE and raise an error. It will *not*, however, prevent a COMMIT.
Here's an example of such a trigger :

SQL> -- create a trigger that raises an error on truncates
SQL> create or replace trigger prevent_truncates
2 before truncate on schema
3 begin
4 raise_application_error(-20001,'TRUNCATE not permitted');
5 end;

How Are Students Learning Programming ?

A recent ComputerWorld article "How are students learning programming in a post-Basic world ?" (It should be BASIC, not Basic) reminds me of the time I first learnt programming.

Yes, with BASIC. When there were very few PCs in Ahmedabad.

Oracle APAC Developer Program

Oracle ACEs in this part of the world had a conference call with Oracle's Program Executive for the APAC Developer Program.

We were provided information about forthcoming DBA Round Table and Developer Day sessions. We were also given assurances that Oracle would continue supporting the ACE program and members.
Thank you, Shaheen.

OOW 2011 Content Catalog

The Oracle Open World 2011 Content Catalog is now available for viewing.


Inequality and NULL

A response recent forums question about handling an inequality condition also reminded me, once again, about NULL handling in Oracle.

You can have :

WHERE column = 100 

in a query.

In another query, you could have

WHERE column != 100 

However, if the column does contain a NULL in any one (or more rows), the union of the two queries is not the entire table. That is, rows with NULLs are excluded.
You have to specifically handle NULLs with either

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