1. Storage Structure and Relationships

2. Database Storage Hierarchy
Tablespace
Data file
Logical
Segment
Physical
Extent
Oracle block
O/S block

3. Database Block: Review
Minimum unit of I/O
Consists of one or more O/S blocks
Set by DB_BLOCK_SIZE
Set at database creation

4. Database Block Contents
Header
Free space
Data

5. Block Space Utilization Parameters
INITRANS
MAXTRANS
PCTFREE
PCTUSED

6. Block Space Usage Inserts Inserts 1 2 Inserts Inserts 3 4
PCTFREE= PCTUSED=40
Inserts
Inserts
80% 1 2
Inserts
80%
Inserts
40% 3 4

7. Organizing Tablespaces Based on Fragmentation Propensity
SYSTEM
TOOLS
DATAn
INDEXn
RBSn
TEMPn
Usage
Data dictionary
Applications
Data segments
Index segments
Rollback segments
Temporary segments
Fragmentation
Zero
Very low
Low
High
Very high*
* Relevant only if tablespace PERMANENT

8. Summary
Allocation and deallocation of extents for different types of segments
Block space utilization parameters