SAP MaxDB on The Lars Breddemann Blog

Answers Pinboard

Mon, 19 Dec 2022 04:33:45 +0000

Apart from writing blog posts I have written answers to many questions on several Q&A sites like StackOverflow and SAP Community. Some of those answers received good feedback and/or the answer surprised me once I worked it out.

New year, same issues and some tips.

Tue, 08 Jan 2019 04:34:44 +0000

Most folks working with SQL DBs for a while will likely come to see how beginners in this area struggle with “declaritive code” and “tell the DB what you want not how to do it”

How to know "all these things"

Tue, 23 Oct 2018 22:29:06 +0000

There is one predominant reason why databases and database technology get a spot in the conversation of “the business”: performance.
Understanding system performance and coming up with ideas for improving it typically requires a form of end-to-end understanding with different levels of detailed insight on how a query from a client application is processed by SAP HANA.

Small changes with big effects

Sat, 29 Jan 2011 14:00:56 +0000

For many BW performance relevant DB-features, it’s really all about the details of usage and implementation when it’s about the effect of those features.

The following are two examples of rather small things that went wrong which had a big impact on the system performance.

MaxDB weekend magic - save 50% total storage space!

Thu, 21 Oct 2010 14:00:38 +0000

People use assumptions to make decisions.

They do this all the time and insofar, developers are people as well :-)

To be a bit more specific, also database developers make assumptions, One of them is for example that when you query data then you ask for data that is actually there. You want to get some data back.

MaxDB Optimizer Statistics handling without NetWeaver

Wed, 26 May 2010 14:00:56 +0000

Ok, MaxDB is most often used with a NetWeaver on top of it, so this blog is about a niche topic of a niche product.
Wow - that should be enough understatement and un-buzzing for now.

MaxDB ST05-trace fallacy - when sometimes the trace is wrong...

Wed, 28 Apr 2010 14:00:36 +0000

One of the most important analytical tools used to investigate slow running SQL statements is the well-known ST05 - SQL trace. The idea of it is that the ABAP database interface notes down what SQL statement it sends to the database, how long it took to get the result, what selection criteria were used and so on.

MaxDB Event Dispatcher Intro

Tue, 12 Jan 2010 14:00:36 +0000

Infrastructure software like RDBMS often tends to become feature-rich in many directions. MaxDB is no exception to this, so by reading the documentation there’s a pretty good chance to dig out some features that are rarely seen or used.

MaxDB – On locking mechanisms and how we learn something new each day… Part II

Mon, 19 Oct 2009 14:00:48 +0000

As I promised here’s the second part of my short excurse into the shoals of lock management with MaxDB databases. (The first part can be found MaxDB - On locking mechanisms and how we get to know our MaxDB a bit better each day… Part I)

MaxDB – On locking mechanisms and how we get to know our MaxDB a bit better each day… Part I

Tue, 13 Oct 2009 14:00:45 +0000

One of the most boring topics within the area of DBMS surely is locking. It’s also one of the topics that most DB users try to avoid as much as possible. Still, it’s utmost important to correctly understand how locking works in the database of choice to be able to work successfully with it and without bad surprises.

Questions to SAP-Support (MaxDB): “Data is gone after reboot – where the heck is it?”

Mon, 10 Aug 2009 14:00:49 +0000

From time to time I start to believe that there are certain problems that would not come up anymore, once the topic is documented well enough. My colleagues from the development know that too well as I’m asking for documentation and notes all the time for everything. However, the written documentation does help nothing if it’s not read…

Questions to SAP Support: “How to prevent MaxDB from creating backups to the RUNDIRECTORY?”

Mon, 29 Jun 2009 14:00:59 +0000

Hello, community!

Just a minute ago I got to work on a message where a customer asked:

“Hello support team, could you please tell me how to teach MaxDB
not to save backups to the default RUNDIRECTORY but to a path specified by me?”

‘Mind the gap…’ (#4 – reading query execution plans)

Sun, 10 May 2009 14:00:28 +0000

In my mini-series " Mind the gap" I will try to shed some light on where the little or big differences between MaxDB and Oracle databases are and what to keep in mind when working with them.

Now step back and start thinking!

Sat, 07 Mar 2009 14:00:41 +0000

The default reaction #

When working in support you get to see a lot of bugs, mistakes and errors.

That’s of course how things are going and there’s not much to whine about.

MaxDB – Space oddities, take II

Mon, 02 Feb 2009 14:00:52 +0000

After the tremendous (and very unlikely) success of the first MaxDB: Space oddities blog, I immediately decided: this must be the voice of the market asking for more.

So here you get it. #

While Oracle DBAs are used to be exposed to features like segment fragmentation (that is, although data is removed from tables/indexes these segments still allocate the same amount of space which won’t be automatically released to the freespace) MaxDB users don’t have to think about this.

MaxDB: Space oddities

Tue, 27 Jan 2009 14:00:55 +0000

MaxDB - Space oddities

Recently a customer came up with the assumption that there is space somehow missing from the database.
Although he deleted a whole lot of data via archiving the data area was still quite filled up.
To investigate he decided to check whether the information visible in DBM GUI are correct.

MaxDB: Some notes on the INDEX_USED statistic

Thu, 20 Nov 2008 14:00:30 +0000

You may have already wondered about whether a specific index is sensible or if you can save space by dropping it.
For this MaxDB provides statistic information in the INDEXES view.
The column INDEXUSED provides the information if the index had been used at all yet and, starting with MaxDB 7.6 it also shows how often an Index has been used.

‘Mind the gap…’ (#3 – Backup/Restore – Part 2)

Sat, 20 Sep 2008 14:00:21 +0000

Before starting with this blog, I’ve to apologize for being so late with this issue of “Mind the Gap”. Since the last part of this series (‘Mind the gap…’ (#3 - Backup/Restore - Part 1)

Questions to SAP Support: “How to move MaxDB volumes?”

Wed, 10 Sep 2008 14:00:57 +0000

Unlike Oracle, MaxDB does not have a CONTROLFILE to store the location of its files.

Instead, all file locations are stored as common parameters.

A quick look at the parameters section of the KNLDIAG reveals this:

Questions to SAP Support: “How to generate a SQL Script via SQL on MaxDB?”

Sun, 10 Aug 2008 14:00:15 +0000

A customer was facing a problem when generating SQL scripts by using SQL. As this is a common habit in the Oracle world he tried to apply it to his MaxDB.

‘Mind the gap…’ (#3 – Backup/Restore – Part 1)

Mon, 23 Jun 2008 14:00:33 +0000

In my mini-series " Mind the gap" I will try to shed some light on where the little or big differences between MaxDB and Oracle databases are and what to keep in mind when working with them.

Questions to SAP Support: “Is my MaxDB recovery still running?”

Tue, 10 Jun 2008 14:00:53 +0000

Today a customer asked about how to monitor recovery activity on MaxDB.

The typical questions here are: " Is it still running?" and " How long will it take?"

While the last question cannot be answered easily (and most often not at all), since the time necessary to finish a recovery largely depends on the performance of the hardware and the data volume, the first question can rather easily be answered.

Questions to SAP Support: Is ODBC access to the database a good idea?

Sun, 18 May 2008 14:00:26 +0000

Today I got a support message to work on that I believe is of rather broad interest.

Therefore, I decided to “forward” it to the SDN so that all community members can benefit from it.

What you don’t know about MaxDB…

Wed, 07 May 2008 14:00:32 +0000

Every day I’m faced with colleagues, customers, partners or SDN members asking questions about MaxDB.

How can we set up an external backup tool? Why is my index not taken by the optimizer? Can I use MaxDB as a productive system?

SDN Wiki Features – what features?

Wed, 12 Mar 2008 14:00:38 +0000

While editing content for MaxDB Wiki here in SDN I wondered how I might return to an older version of the page.

Unlike e.g. MediaWiki http://www.mediawiki.org/ the WIKI engine behind Wikipedia (http://www.wikipedia.org) in the SDN Wiki there is no tab bar “Versions”.

Not my fault – whose then?

Sun, 02 Mar 2008 14:00:04 +0000

I have written some lines about database corruption and the ways to handle them in the past.

The bottom line of everything I wrote (including support notes, SDN blogs, and replies in customer messages) has always been:

Debugging the MaxDB Kernel – How to get a Call stack the easy way

Thu, 07 Feb 2008 14:00:42 +0000

A few months ago, I described how to set up and configure the Windows Debugger in order to be able to generate a call stack for a hanging MaxDB thread (see Debugging the MaxDB Kernel on Windows – How to get a Call stack from hanging tasks).

‘Mind the gap…’ (#2 – Data storage)

Tue, 22 Jan 2008 14:00:08 +0000

More and more customers decide to use MaxDB and with that, the number of customers asking for a comprehensive list of differences or a comparison increases as well.

In my mini-series " Mind the gap" I will try to shed some light on where the little or big differences between MaxDB and Oracle databases are and what to keep in mind when working with them.

Parameters. parameters, parameters … the mantra of db performance troubleshooting

Tue, 15 Jan 2008 14:00:54 +0000

Database performance problems are one of the more complex tasks that brighten the day of a database software supporter.

Each and every single day since I’m doing support for Oracle and MaxDB there had been messages, in which customers complained about bad database performance.

‘Mind the gap …’

Wed, 05 Dec 2007 14:00:54 +0000

More and more customers decide to use MaxDB and with that, the number of customers asking for a comprehensive list of differences or a comparison increases as well.

In my mini-series " Mind the gap" I will try to shed some light on where the little or big differences between MaxDB and Oracle databases are and what to keep in mind when working with them.

MaxDB Internals Documentation available for free!

Sun, 18 Nov 2007 14:00:48 +0000

Today I spoke with Jörg Hoffmeister (Product and Development Manager of MaxDB and liveCache). He told me that finally the " MaxDB Internals" Documentation has been released to the public.

Many thanks for that Jörg!

Debugging the MaxDB Kernel on Windows - How to get a Call stack from hanging tasks

Wed, 14 Nov 2007 14:00:42 +0000

Ok, today I’ll show you how to install, setup and use the Windows Debugger to get information about hanging MaxDB kernel tasks.

The first thing we need is obviously a hanging MaxDB session, so let’s produce one!

A dumb mistake … again and again …

Sat, 20 Oct 2007 14:00:57 +0000

Not to long ago I was analyzing a performance issue on a customers system.
In the course of this I needed to see some aggregated data, so I opened a transaction where I can put in custom sql and ran it without removing the number of lines to be returned limitation.

MaxDB Database Studio 7.7 is available!

Sun, 14 Oct 2007 14:00:50 +0000

I’ve recently written about it (Something new is coming up…).

We presented it on the Las Vegas TechEd (and it will also be shown in Munich).

One question was present all the time: When will the new MaxDB Tool for DBAs/Developers be finally available to the (SAP)-public?

Something new is coming up…

Mon, 24 Sep 2007 14:00:26 +0000

For so many years now the DBMGui and the SQL Studio have been the primary graphical interfaces for developers and DBAs to access MaxDB instances.
Beside the many good features and the relative high stability (i remember the early versions of Oracle’s SQL Worksheet in release 9i…) the major drawback has been the fact that these tools were only available on Windows-Systems.

Blogging standard…

Mon, 03 Sep 2007 14:00:47 +0000

As it seems it has become popular to give his readers a glimpse on the bookshelf like it has been practised by many before me (see here , here or here) I will also reveal what is “behind” me. Literally the books are place on top of a locker behind me…

Suck that data out! Connect from Oracle to MaxDB

Wed, 04 Apr 2007 14:00:39 +0000

In one of my former jobs, I had been in charge of a rather small project tracking tool for the engineering department. As buying equipment and ordering services were two of the duties of these engineers these tasks had also been modelled into the tool. Of course, the orders had to be transported into the central financial application. Therefore a meeting with the consultants for that ERP system (no, not ours… they had got the wrong one there… ;-)) was set up.

I can repair your corrupt database!

Tue, 20 Mar 2007 14:00:36 +0000

Years in database support, endless experience and access to a whole bunch of internal notes and guidelines have enabled me (as well as all DB Supporters in SAP) to repair corrupt databases. This obscure technique is of course only available to the initiated and should be used with care. But when applied it works just like a wand: puff – the database is OK again.

Starting off with a classic…

Tue, 13 Feb 2007 14:00:09 +0000

Every now and then a new version of the database software comes along. Upgrades of Oracle or MaxDB often include major improvements concerning stability and performance. These improvements can and should be read as: things run different now.