Category Archives: DBA

JDBC, Linux and Entropy

Some troubles — especially those happening only sporadically — are not so easy to shoot and call for a deeper understanding of the matter. In the following real-world example this means: SQL*Net Tracing and some knowledge about the inner workings of the server’s operating system, particularly random number generation.

This case was suited well to demonstrate an approach to trouble-shoot connections to Oracle databases.

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Visualizing System Statistics in SQL Developer – OTN Appreciation Day

Tim Hall inspired me with his #ThanksOTN (or “OTN Appreciation Day“) campaign to continue my mini-series on leveraging SQL Developer Reports for DBA tasks. Today with visualizing historical System Statistics from Statspack for performance analyses.

#ThanksOTN I have three favourite Oracle features to rave about today:

  1. Analytic SQL
  2. Statspack
  3. SQL Developer (particularly the reports)!

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Reporting Long Running Operations in SQL Developer

Today here’s a shorter post about my experiments with Oracle SQL Developer’s user-defined reports: A report on all long running operations (“LongOps”) with details on session wait events, explain plans and live SQL monitoring.

“Wait a minute”, you might say, “there’s already the session report in SQL Developer’s standard reports that shows Session_LongOps”! – and you’re right, it’s been integrated in SQLDev for quite some time.

BUT: I wanted to view the LongOps from a different perspective: To find out what’s taking so long in the database generally, it would be better in my humble opinion to start with ALL LongOps and drill down from there.

Here’s how it looks on a live system:

sqldev_longops.png

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Visualizing Statspack “Average Active Sessions” in SQL Developer

This is the second post in my mini-series on leveraging SQL Developer Reports for DBA tasks, today with visualizing Average Active Sessions (AAS). In this article I’ll cover

  • What AAS is and how to interpret it
  • How to build a basic line graph in SQL Developer
  • How to extend the graph with detailed child reports (Time Model Statistics and Top Events)

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Visualizing Statspack Performance Data in SQL Developer

If you run Oracle Standard Edition or haven’t licenced Diagnostics Pack for Enterprise Edition, then you don’t have AWR and ASH Data available. This is when Statspack, the predecessor of AWR, comes in handy to keep a history of database performance metrics.

But although Oracle still deliver Statspack with their recent DB releases (yes, even in 12c it’s not dead!), there are few tools that support it. But wait – Oracle SQL Developer has a nice reporting feature built in, so why not build custom statspack reports for this great free tool?

This motivated me to start a series on leveraging SQL Developer Reports for DBA tasks, starting with visualizing logical I/O history.

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Data Pump and AQ_TM_PROCESSES

First things first:

Thou shalt not explicitly set AQ_TM_PROCESSES=0 !

Unless, of course, you want to disable the Queue Manager Process (QMNC in Oracle 11.x). Which you may want to do during database upgrades to prevent Streams or Advanced Queueing from interfering with the upgrade process.

However, if you don’t reset this parameter afterwards, you might run into the following scenario the next time you do a Data Pump export or import:

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Datapump Bug: Scheduler Jobs Not Imported in 11.2

Just the other day I hit the unpublished Bug 16445132: DBMS_SCHEDULER PROBLEM WITH DATABASE MIGRATION VIA EXPDP/IMPDP.

It affects Scheduler Jobs that were created to end with a corresponding Scheduler Window.

Here’s an excerpt of a Data Pump Logfile:

ORA-39083: Object type PROCOBJ failed to create with error:
ORA-27469: STOP_ON_WINDOW_EXIT is not a valid job attribute

Actually, the correct attribute name for this procedure would be “stop_on_window_CLOSE” instead of “stop_on_window_EXIT”. The latter is an attribute of the JOB_DEFINITION object type which in my eyes is inconsistently named in respect to the SET_ATTRIBUTE procedure.

The bug is fixed, but as of Nov. 2014 there is no one-off patch for version 11.2.0.4. The existing workaround is to ignore the error and recreate the job after the import .

If you run into this bug and it bugs you a lot, the other option is to ask for a patch for this issue.