If you only read one blog post this month, read James Morle’s eloquent attack on the term “Best Practice”. I’m very excited to be joining RittmanMead next month! I’m looking forward to working with some of the industry’s most respected experts.

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In Oracle 11g, the DBMS_STATS procedure GATHER_SCHEMA_STATS takes a parameter ‘options’ which defines the scope of the objects processed by the procedure call, as well as the action. It can be either GATHER or LIST (gather the stats, or list out the objects to be touched, respectively), and AUTO, STALE or EMPTY (defining the object selection to process). GATHER on its own will gather stats on all objects in the schema GATHER EMPTY / LIST EMPTY is self-explanatory - objects with no statistics.

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When using preupgrade to upgrade an existing Fedora 14 installation to Fedora 15, the following two errors were encountered: Failed to fetch release info No groups available in any repository The box sits on a network behind a proxy out to the web. The resolution was to make sure that environment variables http_proxy and https_proxy are set: [sourcecode language=“bash”] export http_proxy=http://user:password@proxyserver:port export https_proxy=http://user:password@proxyserver:port [/sourcecode] Make sure you do this from the user from which you run preupgrade.

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Excel may send chills down the spine of us when we hear users talking about its [ab]use, but it has its place in the toolset. For my money, it is a very good tool for knocking out graphs which look decent. Of course, rrdtool is my geek tool of choice for dynamic long-term graphing, but when doing scratch PoC work, I normally fall back to Excel. One thing which has frustrated me over time is, well, time, and Excel’s handling thereof.

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Here’s a quotation that I’ve just read and wanted to share. It is all part of a BAAG approach to troubleshooting problems, performance in particular. From Greg Rahn (web|twitter) on oracle-l: There are always exceptions, but exceptions can be justified and supported with data. Just beware of the the silver bullet syndrome… The unfortunate part […] is that rarely anyone goes back and does the root cause analysis. It tends to fall into the bucket of “problem…solved”.

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Blogging from Oracle itself about OBIEE has always been a bit sparse, certainly in comparison to that which there is for core RDBMS. It’s good to see a new blog emerge in the last couple of months from OBI Product Assurance, including some nice ’n spicy detailed config/tuning info. Find it here: http://blogs.oracle.com/pa/. There’s a couple more OBI blogs from Oracle, but both are fairly stale: Implementing Oracle BI & EPM Solutions - Rob Reynolds OBIEE Ramblings Oracle BI Foundation (thanks Daan for pointing this one out)

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OK, a bit tired on a Monday morning, and so a bit sarcastic. I’ve not really fallen off my chair, but I am shocked. I honestly didn’t think it would happen. Oracle have finally released OBI 11g for HP-UX Itanium: In other news, patchset 10.1.3.4.2 for OBI 10g was released today, I wonder if/when we’ll get an HP-UX Itanium version? The download page has it conspicuous by its absence even from “Coming Soon”:

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Have you defined CLIENT_ID in your OBIEE RPD yet? You really ought to. As well as helping track down users of troublesome queries, it also tags dump files with the OBIEE user of an offending query should the worst occur: For details, see: Identify your OBIEE users by setting Client ID in Oracle connection Instrumenting OBIEE for tracing Oracle DB calls

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A new version of OBI 10g (remember that?) has just been released, the Oracle twitter machine announced: Along with presumably a bunch of bugfixes, the release notes list new functionality in catalog manager: Download 10.1.3.4.2 from here

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Trying to connect to a repository in ODI using OCI. Target database is Oracle 11.1.0.7. Throws this error: [sourcecode] com.sunopsis.sql.l: Oracle Data Integrator Timeout: connection with URL jdbc:oracle:oci8:@ODIPRD and user ODI_USER. at com.sunopsis.sql.SnpsConnection.a(SnpsConnection.java) at com.sunopsis.sql.SnpsConnection.t(SnpsConnection.java) at com.sunopsis.sql.SnpsConnection.connect(SnpsConnection.java) at com.sunopsis.tools.connection.DwgRepositoryConnectionsCreator.a(DwgRepositoryConnectionsCreator.java) at com.sunopsis.tools.connection.DwgRepositoryConnectionsCreator.a(DwgRepositoryConnectionsCreator.java) at com.sunopsis.graphical.l.oi.a(oi.java) […] [/sourcecode] Normally this error would be caused by a misconfigured Oracle client. For example, a missing or incorrect tnsnames.ora entry. I validated these and got a successful response using tnsping.

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July’s Critical Patch Update from Oracle includes CVE-2011-2241, which affects OBIEE versions 10.1.3.4.1 and 11.1.1.3. No details of the exploit other than it “allows remote attackers to affect availability via unknown vectors related to Analytics Server.” It is categorised with a CVSS score of 5 (on a scale of 10), with no impact on Authentication, Confidentiality, or Integrity, and “Partial+” impact on Availability. So to a security-unqualified layman (me), it sounds like someone could remotely crash your NQSServer process, but not do any more damage than that.

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I noticed on Nico’s wiki (which is amazing by the way, it has so much information in it) a bunch of additional parameters for nqcmd other than those which are displayed in the default helptext (nqcmd -h). These are the additional ones: [sourcecode] -b -w<# wait seconds> -c<# cancel interval seconds> -n<# number of loops> -r<# number of requests per shared session> -t<# number of threads> -T (a flag to turn on time statistics) -SmartDiff (a flag to enable SmartDiff tags in output) -P -impersonate -runas [/sourcecode]

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Here’s a scenario that’ll be depressingly familiar to most reading this: after ages of running fine, and no changes to the code, a query suddenly starts running for magnitudes longer than it used to. In this instance it was an ETL step which used to take c.1 hour, and was now at 5 hours and counting. Since it still hadn’t finished, and the gods had conspired to bring down Grid too (unrelated), I generated a SQL Monitor report to see what was happening: [sourcecode language=“sql”] select DBMS_SQLTUNE.

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There is a well-documented problem relating to DBMS_STATS.COPY_TABLE_STATS between partitions where high/low values of the partitioning key column were just copied verbatim from the source partition. This particular problem has now been patched (see 8318020.8). For background, see Doug Burns’ blog and his excellent paper which covers the whole topic of statistics on partitioned tables. This post Maintaining statistics on large partitioned tables on the Oracle Optimizer blog details what the dbms_stats.

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Chucking a stick in the spokes of your carefully-tested ETL/BI … My opinion is that automated stats gathering for non-system objects should be disabled on Oracle Data Warehouses across all environments. All it does it cover up poor design or implementation which has omitted to consider statistics management. Once you get into the realms of millions or billions of rows of data, the automated housekeeping may well not have time to stat all of your tables on each run.

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Just because something produces the correct numbers on the report, it doesn’t mean you can stop there. How you are producing those numbers matters, and matters a lot if you have an interest in the long-term health of your system and its ability to scale. OBIEE is the case in point here, but the principle applies to any architecture with >1 tiers or components. Let me start with a rhetorical question.

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Chris Mellor at The Register posted an interesting article a couple of days ago, entitled HP and Violin build Oracle Exadata killer. The slidedeck has been removed from HP’s FTP site, but a bit of Google magic throws up a couple of mirror copies. It’s an entertaining read (“Do a Proof of Concept! 94% win rate!! We can and do win against Exadata!!”), and a nice illustration of the FUD techniques that companies use in marketing their products against others.

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Whilst perusing the Oracle database documentation, I noticed something which caught my eye: As well as reading the documentation online as HTML or downloading as PDF for viewing on your computer etc, you can also download it in formats (Mobi and ePub) designed for eReaders such as the Kindle and iPad (the latter obviously isn’t “just” an eReader). For information on format support, there’s a handy table on Wikipedia. It looks like the availability of mobi/epub files isn’t universal.

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Oracle XE 11gR2 beta has just been released, some details here and download here. It’s not a great deal of use for sandboxing DWH-specific stuff, given this list of excluded functionality (and this is by no means everything that’s not included): Bitmapped index, bitmapped join index, and bitmap plan conversions Oracle Partitioning Parallel Data Pump Export/Import Parallel query/DML Parallel Statement Queuing (source) However, it’s always interesting to have to hand for trying out other things.

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This post expands on one I made last year here about sampling frequency (of I/O throughput, but it’s a generic concept). The background to this is my analysis of the performance and capacity of our data warehouse on Oracle 11g. Before I get too boring, here’s the fun bit: Pork Pies per Hour (PP/h) Jim wants to enter a championship pork-pie eating competition. He’s timed himself practising and over the course of an hour he eats four pork pies.

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