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5 Managing Database Storage Structures

After completing this lesson, you should be able to d the following: • Describe how table row data is stored in blocks • Define the purpose of tablespaces and data files • Create and manage tablespaces • Obtain tablespace information • Describe the main concepts and functionality of Automatic Storage Management (ASM) | Managing Database Storage Structures Oracle Database 10g: Administration Workshop I 5- Objectives After completing this lesson, you should be able to do the following: Describe how table row data is stored in blocks Define the purpose of tablespaces and data files Create and manage tablespaces Obtain tablespace information Describe the main concepts and functionality of Automatic Storage Management (ASM) Oracle Database 10g: Administration Workshop I 5- Storage Structures Database Tablespace Segment Extent Oracle data block Logical Physical OS block OS file Storage Structures A database is divided into logical storage units called tablespaces. Each tablespace has many logical Oracle data blocks. The DB_BLOCK_SIZE parameter specifies how large a logical block is. A logical block can range from 2 KB to 32 KB in size. The default size is 8 KB. A specific number of contiguous logical blocks form an extent. A set of extents that are allocated for a certain logical structure form . | Managing Database Storage Structures Oracle Database 10g: Administration Workshop I 5- Objectives After completing this lesson, you should be able to do the following: Describe how table row data is stored in blocks Define the purpose of tablespaces and data files Create and manage tablespaces Obtain tablespace information Describe the main concepts and functionality of Automatic Storage Management (ASM) Oracle Database 10g: Administration Workshop I 5- Storage Structures Database Tablespace Segment Extent Oracle data block Logical Physical OS block OS file Storage Structures A database is divided into logical storage units called tablespaces. Each tablespace has many logical Oracle data blocks. The DB_BLOCK_SIZE parameter specifies how large a logical block is. A logical block can range from 2 KB to 32 KB in size. The default size is 8 KB. A specific number of contiguous logical blocks form an extent. A set of extents that are allocated for a certain logical structure form one segment. An Oracle data block is the smallest unit of logical I/O. Oracle Database 10g: Administration Workshop I 5- How Table Data Is Stored Tablespace Table A Table B Segment Segment Rows Columns Table Blocks Row piece Extent How Table Data Is Stored When a table is created, a segment is created to hold its data. A tablespace contains a collection of segments. Logically, a table contains rows of column values. A row is ultimately stored in a database block in the form of a row piece. It is called a row piece because under some circumstances the entire row may not be stored in one place. This happens when an inserted row is too large to fit into a single block or when an update causes an existing row to outgrow its current space. Oracle Database 10g: Administration Workshop I 5- Anatomy of a Database Block Block header Free space Row data Growth Database Block: Contents Oracle data blocks contain the following: Block header: The block header contains the segment type (such