tuning

SQL Server: why can’t I read the full table in parallel???

Why SQL Server keeps a full SELECT * serial: I/O cost is never divided across threads. Forcing parallelism burned 3x the CPU.

Apache httpd Tuning and Monitoring with Zabbix

There is no tuning possible without a proper monitoring in place to measure the impact of any changes. Thus, before trying to tune an Apache httpd server, I will explain how to monitor it with Zabbix. Setup Zabbix Monitoring(…)

SELECT FROM DUAL : Oracle Performance And Tuning

The DUAL table is automatically created by Oracle and contains one column (DUMMY) and one row (x value). This table is often used by SQL developer in PL/SQL code (Package, Functions, Trigger) to initialize variables storing technical information such as(…)

PGIO, PG_STAT_ACTIVITY and PG_STAT_STATEMENTS

By Franck Pachot . For an Oracle DBA, we are used to join active sessions (from V$SESSION where status='ACTIVE) with active statements (from V$SQL where users_executing>0) on the SQL_ID. V$ACTIVE_SESSION_HISTORY also displays the TOP_LEVEL_SQL_ID to get the entrypoint of the(…)

Experiencing update statistics on a big table with circuitous ways

This is my first blog of this new year and since a while by the way. Indeed, last year, I put all my energy to realign my Linux skills with the new Microsoft’s strategy that opens SQL Server to Open(…)

Dynamic Sampling vs. Extended Statistics

By Franck Pachot . On datawarehouse databases, I frequently recommend increasing the level of dynamic sampling because: Queries have complex predicates with AND, OR, IN(), ranges and correlated values for which the optimizer cannot estimate the cardinality properly Queries are(…)

Documentum xPlore: Tuning of JVM for high throughput and low CPU usage

Sometimes you have java processes or even jboss servers using a lot of CPU. In my example I had an xPlore dsearch server using like 98% of the cpu. When using jconsole and jvisualvm I figured out the garbage collector(…)