OK, so while trying to understand Oracle’s redo latching mechanisms (we have been experiencing a nightmare with log file sync since switching to a new DMX subsystem), I found that java 1.5 has a new Lock class. How cool is…
Standby created without a standby controlfile?!!
Today, a junior DBA created a standby database by copying the controlfile to another host, restoring the 4TB database it serves, and recovering all available logs via RMAN. Sounds good, right? Well, it was until we went into SQL*PLUS and…
Read only tablespace requires no outstanding transactions…anywhere…
Nice little gotcha I received yesterday morning. Our intention is to rebuild two large tables from range partitioning to hash partitioning on another server. One of the datafiles for the tablespace that houses one of the tables in question is…
Oracle function to calculate wait event correlation
Cool little function to provide statistical correlation between two events. This helped us to identify performance drivers in our database. Statistically, anything above 60 is considered “statistically significant”, or correlated. If one goes up, so does the other. create or…
Statistical functions with java
Below is a simple set of classes for performing your own statistical analysis. As noted, they are simple (no multiple regression analysis, etc.) class myStats { double standardDeviation (double[] array) { double[] arr = new double[array.length]; double av = average(array);…
Control file writes when updating???
I had never seen this before, but while testing a migration strategy for a large table with XMLTYPE’s, almost half our wait time was spent on control file sequential read and control file parallel write waits. Each of these occurred…