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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.

What’s new with Oracle database 18.7 versus 18.6

With the Oracle database version 18.6 patched to 18.7 on linux, the following things have changed:

Resumable

There are two questions about temporary space that appear fairly regularly on the various Oracle forums. One is of the form:

From time to time my temporary tablespace grows enormously (and has to be shrunk), how do I find what’s making this happen?

The other follows the more basic pattern:

My process sometimes crashes with Oracle error: “ORA-01652: unable to extend temp segment by %n in tablespace %s” how do I stop this happening?

Before moving on to the topic of the blog, it’s worth pointing out two things about the second question:

Video : Oracle REST Data Services (ORDS) : AutoREST

Today’s video is a demonstration of the AutoREST feature of Oracle REST Data Services (ORDS).

This is based on the following article.

I also have a bunch of other articles here.

The star of today’s video is Connor McDonald of “600 slides in 45 minutes” fame, and more recently AskTom

Cheers

What’s new with Oracle database 12.2.0.1.190416 versus 12.2.0.1.190716

There are a couple of underscore parameters changed from spare to named ones.
It’s interesting to see that in sysstat, ‘spare statistic 2’ changed to ‘cell XT granule IO bytes saved by HDFS tbs extent map scan’. This obviously has to do with big data access via cell servers. What is weird is that this is the only version where this had happened.

opt_estimate catalogue

This is just a list of the notes I’ve written about the opt_estimate() hint.

My Oracle Support (MOS) : Where do we go from here?

Well, it happened again. I lost the plot on Twitter … again. I deleted them a lot quicker this time, but a few people saw them … again…

Today’s “incident” was because I was juggling multiple SRs, where I don’t think I’m getting straight answers, and what I believe is a reasonable level of service.

Having deleted the tweets I put out this one.

I am venting because I have no filter these days, and I am quickly deleting them because I know they will cause problems for some of my friends inside Oracle.

I feel like I want to go to war over this, but I know the best thing to do is to go home and play with tech…

What’s new with Oracle database 12.1.0.2.190416 versus 12.1.0.2.190716

There are a couple of undocumented spare parameters changed to named undocumented parameters, this is quite normal to see.

With the Oracle database version 12.1.0.2.190416 patched to 12.1.0.2.190716 on linux, the following things have changed:

Trace Files

A recent blog note by Martin Berger about reading trace files in 12.2 poped up in my twitter timeline yesterday and reminded me of a script I wrote a while ago to create a simple view I could query to read the tracefile generated by the current session while the session was still connected. You either have to create the view and a public synonym through the SYS schema, or you have to use the SYS schema to grant select privileges on several dynamic performance views to the user to allow the user to create the view in the user’s schema. For my scratch database I tend to create the view in the SYS schema.

Script to be run by SYS:

_cursor_obsolete_threshold

At the recent Trivadis Performance Days in Zurich, Chris Antognini answered a question that had been bugging me for some time. Why would Oracle want to set the default value of _cursor_obsolete_threshold to a value like 8192 in 12.2 ?

In 11.2.0.3 the parameter was introduced with the default value 100; then in 11.2.0.4, continuing into 12.1, the default value increased to 1,024 – what possible reason could anyone have for thinking that 8192 was a good idea ?

The answer is PDBs – specifically the much larger number of PDBs a single CBD can (theoretically) support in 12.2.

In fact a few comments, and the following specific explanation, are available on MoS in Doc ID 2431353.1 “High Version Counts For SQL Statements (>1024) Post Upgrade To 12.2 and Above Causing Database Slow Performance”: