Access Path
Mandatory.
Specify the method to be used to maintain the IBM i database access path associated with this logical view/file.
When a logical view is created to arrange the information in a file into a specific order, the IBM i database creates an access path.
The access path is essentially the logical file "key fields" arranged in a special structure that allows:
- Extremely fast access to any individual record in the file using just the key(s) of the logical file.
- The processing of the records in order of the logical file key(s) without the need to first sort the file.
An access path exists for every logical view/file created. Every time a record in the file is added, deleted or updated the operating system must update all the access paths to this file. To do this it must use up part of the computer's time and available processing cycles. This of course degrades the performance of the system. The more access paths that are being maintained, the slower the system will run.
Default=Immediate.
Rules
Allowable values are:
|
IMMED |
The access path should be maintained immediately (i.e. whenever a record is added, updated or deleted from the file). This option is the most common. If the logical file is to be used in an interactive environment then IMMED should always be used. |
|
DELAY |
The access path should only be maintained when the logical file is used. This type of access path lies dormant and is not maintained by the operating system until such time as someone needs to use the logical file. Thus it places no burden on the operating system until it is actually required. Typically, logical views that use this option are only used very infrequently to "sort" a file into a specific order. |
Platform Considerations
- IBM i: This file attribute applies to IBM i databases only.
Tips & Techniques
- If the logical file is to be used in an interactive environment, then this option should be selected.