EVI maintenance

 

There are unique challenges to maintaining EVIs. The following table shows a progression of how EVIs are maintained and the conditions under which EVIs are most effective and where EVIs are least effective based on the EVI maintenance characteristics.

Table 1. EVI Maintenance Considerations

	Condition	Characteristics
Most Effective Least Effective	When inserting an existing distinct key value	Minimum overhead Symbol table key value looked up and statistics updated Vector element added for new row, with existing byte code
	When inserting a new distinct key value - in order, within byte code range	Minimum overhead Symbol table key value added, byte code assigned, statistics assigned Vector element added for new row, with new byte code
	When inserting a new distinct key value - out of order, within byte code range	Minimum overhead if contained within overflow area threshold Symbol table key value added to overflow area, byte code assigned, statistics assigned Vector element added for new row, with new byte code Considerable overhead if overflow area threshold reached Access path validated - not available EVI refreshed, overflow area keys incorporated, new byte codes assigned (symbol table and vector elements updated)
	When inserting a new distinct key value - out of byte code range	Considerable overhead Access plan invalidated - not available EVI refreshed, next byte code size used, new byte codes assigned (symbol table and vector elements updated

 

Parent topic:

Encoded vector indexes