Enabling constraint in parallel

Recently I did some tuning of data generation scripts, which purpose is to build large amount of representative data for application testing. Direct-path inserts are in use and as a prerequisite all constraints and indexes on target tables are disabled before the load and are enabled after it. Since I wanted to utilize available resources on the machine for that task, almost each step uses parallel execution. Well, kind of almost, because enabling constraints didn’t run in parallel, although I’ve politely asked Oracle to do so. I’ll explain here why it didn’t work.

PQ_DISTRIBUTE enhancement – Part 1

Oracle 11g has introduced a hell lot of new features related to Parallel Execution – like statement queuing, in-memory PX and auto-DOP, to name a few. There are also small bits of enhancements here and there – like default value of the PARALLEL_EXECUTION_MESSAGE_SIZE and an introduction of an easy way to stick PX slaves to a current RAC node with PARALLEL_FORCE_LOCAL. As I’ve recently discovered, PQ_DISTRIBUTE hint used only for joins prior to 11gR2, can now be used for load operations.

Enhanced Subquery Optimizations in Oracle

While googling I found a fresh article from Oracle for the VLDB journal: Enhanced Subquery Optimization in Oracle. It primarily discusses subqueries – how Oracle deals with them on optimization and at run-time.

RAC is not a requirement for in-memory PX

As pointed out by Greg Rahn in the comments to Mark Rittman’s blog post, new Oracle 11gR2 feature called In-Memory Parallel Execution work well in a single-instance environment.