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External table preprocessor on Windows

There are plenty of blog posts about using the pre-processor facility in external tables to get OS level information available from inside the database. Here’s a simple example of getting a directory listing:

Worth the wait

Yes, I know it’s been awhile Smile

Yes, I know people have been angry at the delay Smile

But, can we put that behind us, and rejoice in the fact…that YES

It’s here!

Yes, 18c XE for Windows is now available.

https://www.oracle.com/technetwork/database/database-technologies/express-edition/downloads/index.html

Statistics on Object tables

Way back in Oracle 8.0 we introduced the “Object-Relational” database, which was “the next big thing” in the database community back then. Every vendor was scrambling to show just how cool their database technology was with the object-oriented programming paradigm.

Don’t get me wrong – using the Oracle database object types and features associated with them has made my programming life a lot easier over the years. But for me, it’s always been pretty much limited to that, ie, programming, not actually using the object types in a database design as such. Nevertheless, using objects as columns, or even creating tables of objects is supported by the database. For example, I can create a object type of MY_OBJECT (which could itself be made up of objects) and then have a table, not with that object as a column, but actually a table of that object.

DBMS_JOB is an asynchronous mechanism

One of the very cool things about DBMS_JOB is that a job does not “exist” as such until the session that submitted the job commits the transaction. (This in my opinion is a critical feature that is missing from the DBMS_SCHEDULER package which, other than this omission, is superior to DBMS_JOB in every way).

Because DBMS_JOB is transactional, we can use it to make “non-transactional” things appear transactional. For example, if part of the workflow for hiring someone is to send an email to the Human Resources department, we can do the email via job submission so that an email is not sent if the employee record is not created successfully or is rolled back manually, eg:

Patch conflicts

My last post was about patching my home databases from 18.3 to 18.5 on Windows, and how I encountered a patch conflict when I tried to patch the JVM. I thought I’d give a little bit of info for anyone who runs into patch conflicts from time to time. It can be stressful especially if unforeseen, or you are in the middle of limited time outage window etc.

So before you jump into applying a patch, a nice little tool you might like to explore is the patch conflict checker on My Oracle Support. You can get it via:

https://support.oracle.com/epmos/faces/PatchConflictCheck

It is straightforward to use, you simply fill in the platform and your current patch inventory details, and then list out the patches you intend to apply.

From Database 18.3 to 18.5 (on Windows)

Contrary to wild rumours on the internet, it was not a fear of the number 13 that led to a numbering jump from version 12c to version 18c. The jump was part of our new, more flexible release mechanism so that we can get fixes and enhancements to customers on a more frequent and predictable schedule. In a nutshell, smaller bundles of features and fixes, more frequently.

I won’t dwell on that – if you’re unfamiliar with the new strategy, the best place to start is  MOS Note 2285040.1, which has a description and a FAQ. But in terms of (as the saying goes) eating one’s own dog food, I downloaded the 18.5 release update which came out this week, and applied it to my 18.3 installation and I thought I’d share the process.

EXPORT not GATHER with DBMS_STATS

Just a short post today on something that came in as a question for the upcoming Office Hours session which I thought could be covered quickly in a blog post without needing a lot of additional discussion for which Office Hours is more suited to.

The question was:

“When I gather statistics using DBMS_STATS, can I just create a statistic table and pass that as a parameter to get the results of the gather”

And the answer simply is “No” Smile but let me clear up the confusion.

Your New Years Resolution

Aligning roughly with the calendar year, based on the Chinese zodiak we’re about to go from the year of the dog to the year of the pig. But for me, in the “Information Technology Zodiak” Smile , 2018 was the year of the hack, just as it was in 2017 and just as it will be for 2019.

I’ve not dedicated much time to keeping a record of all of the high profile breaches this year, but just off the top of my head I can think of:

Automatic sequences not being dropped

One of the nice new things in 12c was the concept of identity columns. In terms of the functionality they provide (an automatic number default) it is really no different from anything we’ve had for years in the database via sequences, but native support for the declarative syntax makes migration from other database platforms a lot easier.

Under the covers, identity columns are implemented as sequences. This makes a lot of sense – why invent a new piece of functionality when you can exploit something that already has been tried and tested exhaustively for 20 years? So when you create a table with an identity column, you’ll see the appearance of a system named sequence to support it.

The phantom tablespace

(Cueing my deep baritone Morpheus voice…) What if I told you that you can reference non-existent tablespaces in your DDL?

OK, it sounds like a gimmick but there is a real issue that I’ll get to shortly. But first the gimmick Smile

I’ve created a partitioned table called “T” (I’ll pause here for your applause at my incredible imagination skills for table naming Smile) and to show you the complete DDL, I’ll extract it using the familiar DBMS_METADATA package.