A tip I picked up from Nigel Bayliss regards purging SQL Plan Directives, I’ve been using it a lot recently and can’t see it documented elsewhere. As some background these records, exposed via the DBA_SQL_PLAN_DIRECTIVES view, are cardinality corrections created and used when running with Adaptive Statistics enabled. There is a job that should automatically …
Recently I’ve been working with SQL Server and while it’s not all bad, sometimes it does helps to highlight some of the neat features available in Oracle. One of these is IMPLICIT cursors, which I shall demonstrate. First I’ll show how to populate some data in a table and then loop over it in TSQL …
I’ve been playing around with researching ORDS over the summer particularly trying to optimize performance on Tomcat. Trying something a little different I’ve created a Vagrant box that should allow anybody interested to verify my findings, find mistakes I’ve made or identify performance optimizations I’ve missed. If you’re new to Vagrant, Tim Hall provides a …
Preparing for my talk at the HK Open Source Conference I wanted to confirm some of the things I had read about these plugins, mostly from Matthias Crauwels excellent article on the subject. My lab environment consists of Windows 2016 Domain controller and client machines, with MySQL 8 running on Oracle Linux 7. First I …
mysql_clear_password & authentication_ldap_simple password encryption Read More »
Recently some of our developers have moved forwards with fixing some code that has been using literals, instead of bind variables. A complication is that they are using lists of values, so the SQL they were generating was of format WHERE COL1 IN (1,2,3,4) They resolved this by using an array in Java and construct …
Invalid SQL being sent to the database is something to watch out for, it’s a real performance killer because once SQL is rejected by parser, it is not cached in shared pool, resulting in hard parse every time the SQL is encountered. One cool new feature of Oracle 12.2 is the fact that such SQL …
Fun with SQL Translation Framework – By-Passing Parse Errors Read More »
The behavior of the LAST_LOGIN field on DBA_USERS has changed with respect to proxy authentication (for the better I think). Proxy authentication is an feature of the Oracle Database that effective allows you to be connected as one user (the client user to use Oracle’s terminology), but using the credentials of another user (the proxy …
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After implementing a recent change, and I pulled of a quick AWR report to compare performance. At first glance I was impressed by significant improvement in “log file parallel write” event, which had halved from 2 millisecond to 1 millisecond, but something about the numbers didn’t quite look right. Before: After: Let’s calculate the average …
Update (2018-07-28) Lukas Eder highlighted via twitter that my comparison was invalid dues to some PL/SQL optimizations. I have updated the testcase, there is still significant improvement, just not as much as my previous test Recently I’ve been noticing a lot of frequently called PL/SQL code that has structure similar to the following: SELECT TO_CHAR(l_date, …