Podcast
Questions and Answers
What is the primary method to reduce disk I/O and improve database performance?
What is the primary method to reduce disk I/O and improve database performance?
- Database tuning
- SQL commands
- Indexing (correct)
- Clustering
When a user query uses an indexed column, what does ORACLE do?
When a user query uses an indexed column, what does ORACLE do?
- Automatically uses the index (correct)
- Ignores the query
- Reads the entire table
- Uses clustering techniques
What are the two common ways to improve the performance of database tables?
What are the two common ways to improve the performance of database tables?
- Normalization and Denormalization
- Joins and Subqueries
- Partitioning and Replication
- Indexing and Clustering (correct)
Which method does ORACLE use to find specific records with minimal disk I/O?
Which method does ORACLE use to find specific records with minimal disk I/O?
What kind of columns are indexes most useful for?
What kind of columns are indexes most useful for?
How do Indexing and Clustering differ in improving database performance?
How do Indexing and Clustering differ in improving database performance?
Why can unnecessary indexes slow down a database system?
Why can unnecessary indexes slow down a database system?
How does clustering help improve database performance?
How does clustering help improve database performance?
What is the purpose of an index in a database?
What is the purpose of an index in a database?
When is an index automatically used in ORACLE?
When is an index automatically used in ORACLE?
What happens if an index is dropped from a table?
What happens if an index is dropped from a table?
What is the purpose of creating a unique index on a column in a table?
What is the purpose of creating a unique index on a column in a table?
Study Notes
Database Performance Tuning
- Database performance is a major user demand after application startup.
- Two common ways to improve database performance are indexing and clustering.
Indexing
- Indexing is a primary method to reduce disk I/O and improve database performance.
- An index is used automatically by Oracle when the indexed column is in a query.
- Indexes quickly find specific records using the index, reducing disk I/O.
- Without an index, Oracle has to read the entire table to find a specific record.
- Indexes are useful only for frequently accessed key columns.
- Unnecessary indexes can slow down the system and database performance.
- Indexes need to be updated with every operation, adding storage and processing burdens.
Creating an Index
- An index is created using the CREATE INDEX command.
- The syntax is:
CREATE [UNIQUE] INDEX [schema.]indexname ON tablename (column1, column2 …); - Schema specifies the name of the schema that contains the index.
- Indexname specifies the name of the index to be created.
- Tablename specifies the name of the table on which the index is created.
- Column1, column2 … specify the names of columns from tables on which the index is to be created.
- UNIQUE specifies that the value of the column (or combination of columns) in the table to be indexed must be unique.
Dropping an Index
- An index can be dropped when it is no more required.
- The syntax is:
DROP INDEX [schema.]indexname
Clustering
- Clustering is another method of improving database performance.
- Clustering stores data together from different tables that are often accessed together.
- Clustering boosts performance for tables often used in join queries.
- This reduces data retrieval time because joined rows are stored together.
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Description
Learn about indexing and clustering techniques to improve database performance. Understand how indexing reduces disk I/O and enhances query performance. Explore the differences between indexing and clustering methods.
