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v$object_usage catches me out every time :-)

Every …. single …. time….
Why does index monitoring make me scratch my head and charge off to google so many times…Well, I’m over it, so time to put it on my blog (even though its already on many other places) so I do not get caught out anymore :-)
It always starts like this:

Just another example - Writing efficient SQL with analytic function

I have a monitoring job set up to alert me when the buffer gets per execution of a SQL above certain threshold. Today I received one as below:

start : 13-MAR-15 PM
end : 13-MAR-15 PM
snapid from 107851 to 107853

list sql with buffer gets per execution > 100000

Parallel Execution -- 2b PX Servers

Continuing my previous post, here I demonstrate  using V$SQLSTATS.PX_SERVERS_EXECUTIONS and a couple of issues around it.

I have restarted the database.

[oracle@localhost ~]$ sqlplus hemant/hemant

SQL*Plus: Release Production on Fri Mar 13 22:49:20 2015

Copyright (c) 1982, 2010, Oracle. All rights reserved.

Connected to:

ORA-27300: OS system dependent operation:fork failed with status: 12 in Solaris SPARC 11

/u01/app//oracle/11.2.0/admin/PROD_mytest/diag/rdbms/prod/PROD/trace/PROD_ora_6122.trc  (incident=69105):ORA-04030: out of process memory when trying to allocate 4128 bytes (kxs-heap-c,temporary memory)Use ADRCI or Support Workbench to package the incident.See Note 411.1 at My Oracle Support for error and packaging details.Fri Mar 13 15:43:12 2015Sweep [inc][69105]: completedFri Mar 13 15:43:12 2015Process startup failed, error stack:

Friday Philosophy – My Introduction To Programming Way Back When

One fortunate thing about me is my age. Or rather, how old I was in the 1980’s. I was at school in the 80’s, I did my ‘O’ Levels (taken at age 16) in 1984. One of my ‘O’ levels was in Computer Studies. This was before Windows and Excel and Word and all that office software, before the internet was in existence (TCP/IP was only standardized in 1982!) and phones were all tethered to the wall with a cable. What were we taught in Computer Studies? Programming. That and a bit about hardware, but mostly it was programming.

Not NULL Constraint Influences Access Path

RSS content
The optimizer can make use of explicitly defined Not NULL constraints to take advantage
of an index in order to avoid a full table scan since a B-tree index stores only not NULL values .
When  count (constant) or count(*)  is queried,  we want to count no. of rows in the table. Hence , if there is a column which is defined as not NULL and has an index on it, the number of index entries  in the index are bound to be same as the number of rows. The query optimizer uses the index to count no. of rows in the table.

12c Parallel Execution New Features: Concurrent UNION ALL - Part 2

In the first part of this series I've focused on the parallel degree chosen by the optimizer when dealing with the new concurrent UNION ALL feature.I've shown that for the variant with serial branches only in the UNION ALL in principle the number of branches dictates the parallel degree determined, even in cases of more complex plans that mix such a serial branch only UNION ALL operator with some other parallel stuff for example via a join.In this part I'll focus on the r

comment in external table

Depending the files, you may use different signs for comments, typically

# hash
// slash slash 
/* slash-star star-slash */
: column
-- dash dash

Extra-cost Option?

"Just because you have a choice, it doesn't mean that any of them 'has' to be right."
Norton Juster, The Phantom Tollbooth

In an Oracle forum that I frequent a user posted that he found cardinality values to be severely inflated when using an analytic function. This user posted an example that will be used here to demonstrate the problem. It will also be used to demonstrate another issue that can make this problem even more confusing, but the latter issue is one that can easily be fixed.

All commenters now welcome

I've finally bitten the bullet and disabled the Google+ commenting mechanism from this blog. I promised this in my 2014 annual review, and I figure I might as well not wait.
When Google announced they would integrate Google+ with blogger, it sounded like a good idea at the time. However it required that commenters needed a Google+ account as opposed to having a number of authentication options.
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