Oracle

Jonathan Lewis's picture

Clustering_Factor

Originally drafted July 2018

“How do you find out what the clustering_factor of an index would be without first creating the index ?”

I’m not sure this is really a question worth asking or answering[1], but since someone asked it (and given the draft date I have no idea who, where, when or why), here’s an answer for simple heap tables in the good old days before Oracle made public the table_cached_blocks preference. It works by sorting the columns you want in the index together with the table rowid, and then comparing the file/block component of the rowid (cutting the relevant characters from the string representation of the rowid) with the previous one to see if the current row is in the same block as the previous row.  If the row is in a different block we count one, otherwise zero.  Finally we sum the ones.

dbakevlar's picture

Oracle on Azure- Options, Options, Options

I’ve been very busy allocating 60% of my time towards Oracle on Azure migrations.  The biggest challenge right now isn’t getting Oracle on Azure, but keeping my percentage of time allocated to only 60%.

oraclebase's picture

Video : Oracle REST Data Services (ORDS) : Create Basic RESTful Web Services Using PL/SQL

Today’s video is a brief run through creating RESTful web services using Oracle REST Data Services (ORDS) and PL/SQL.

This is based on the following article, but the article has a load more examples and variations compared to the video.

I don’t mention handling complex payloads or status information, but you can find that here.

Jonathan Lewis's picture

v$session

Here’s an odd, and unpleasant, detail about querying v$session in the “most obvious” way. (And if you were wondering what made me resurrect and complete a draft on “my session id” a couple of days ago, this posting is the reason). Specifically if you want to select some information for your own session from v$session the query you’re likely to use in any recent version of Oracle will probably be of the form:


select {list for columns} from v$session where sid = to_number(sys_context('userenv','sid'));

Unfortunately that one little statement hides two anomalies – which you can see in the execution plan. Here’s a demonstration cut from an SQL*Plus session running under 19.3.0.0:

oraclebase's picture

OGB Appreciation Day 2019 : It’s a Wrap (#ThanksOGB)

Yesterday was the Oracle community OGB Appreciation Day 2019.

I would like to say a big thank you to everyone who took the time to join in. Here is the list of posts I saw in chronological order. If I missed you out, give me a shout and I’ll add you. </p />
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oraclebase's picture

OGB Appreciation Day : Infrastructure is dead. It’s all about the platforms baby! (#ThanksOGB)

Here’s my entry for OGB Appreciation Day 2019

If you’ve followed me in recent times, you’ve probably heard me say something like this.

“Infrastructure is dead. It’s all about the platforms baby!”

I might not have added the “baby” though. </p />
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Franck Pachot's picture

OGB Appreciation Day : “_query_on_physical” (again)

OGB Appreciation Day : “_query_on_physical” (again)

Looks like we are on the #ThanksOGB day.

One place where the Oracle Community is great is when it helps users with the technology, far from the commercial considerations. We all know that it can be very easy to use some features that are not covered by the license we bought, and this can cost a lot in case of an LMS audit. Here is a post about trying to avoid to activate Active Data Guard option by mistake, as there were many attempts to find a solution in the community.

Jonathan Lewis's picture

My SID

Here’s a little note that’s been hanging around as a draft for more than eight years according to the OTN (as it was) posting that prompted me to start writing it. At the time there were still plenty of people using Oracle 10g. so the question didn’t seem entirely inappropriate:

On 10g R2 when I open a sqlplus session how can I know my session SID ? I’m not DBA then can not open as sysdba and query v$session.

fritshoogland's picture

What’s new with Oracle database 19.4 versus 19.3

The most notable thing here is an “official” (non-underscore) parameter has been introduced with 19.4, “ignore_session_set_param_errors”. The description is: ‘Ignore errors during alter session param set’. I did a quick check to see if I could set it to true or false, which I couldn’t (resulted in an error).

With the Oracle database version 19.3 patched to 19.4 on linux, the following things have changed:

martin.bach's picture

orachk can now warn about unwanted cleanup of files in /var/tmp/.oracle

Some time ago @martinberx mentioned on twitter that one of his Linux systems suffered from Clusterware issues for which there wasn’t a readily available explanation. It turned out that the problem he faced were unwanted (from an Oracle perspective at least) automatic cleanup operations in /var/tmp/.oracle. You can read more at the original blog post.

The short version is this: systemd (1) – successor to SysV init and Upstart – tries to be helpful removing unused files in a number of “temp” directories. However some of the files it can remove are essential for Clusterware, and without them all sorts of trouble ensue.

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