July 2015 archive

As the topic before, execution plans are another thing that just the practical experience will give you knowledge. Studying through docs is not a good approach to learn that, at least for me. After you get the basic concepts, try to check and understand what and why is happening. Study also: Creating Plan Table. Set explain from …

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Access Methods (or Paths) are something totally related to the optimizer. So, what you should study here are the access methods that are possible inside Oracle for either Tables, B-Tree Indexes, Bitmap Indexes or Clusters: Full Table Scans Table Access by Rowid Sample Table Scans Index Unique Scans Index Range Scans Index Full Scans Index Fast …

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Resource Manager is very very useful when you want to limit your system resources. Sometimes you can have a session that is out of control taking all your parallels servers or consuming a lot of CPU and I/O. Or even if you want to limit ("give a quota") the UNDO tablespace consumption by someone. So, …

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I've already talked about this topic here and here. Basically we have 2 types of partitioned indexes: GLOBAL and LOCAL: Local Partitioned Indexes. Local indexes can only be unique if the partitioning key is a part of the index key. A bitmap index on a partitioned table must be a local index. Global Partitioned Indexes. Note here …

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Multi column is another item any DBA must know about. It's very important on tables where you have 2 columns that are correlated. So you must tell the optimizer that! The classical example for that is: How many people have a birth month of May? How many people have a Zodiac sign of Taurus? How …

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