Database Management
Reference Manual
Introduction to Database Concepts
:
Multiwrite Working
: Multiwrite Strategy
Multiwrite Strategy
The Database employs two techniques to allow multiple writers.
A claiming mechanism - User must claim an element at the point of making a modification. This will lock the element preventing other users making modifications.
A Last Back Wins strategy- For some changes a 'last back win' strategy is used rather than claim locks. With this strategy two users may change the same element. Any changes are merged back in. The merging is done at the attribute level. If two users change the same attribute then the last save wins. Places where this strategy is used are:
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Some connection attributes. e.g changing a TREF attribute on a branch does not require the BRANCH to be claimed.
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Member lists containing primary elements are always merged back. e.g. creating a ZONE below a SITE doe NOT require the SITE to be claimed,
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Changes issued from variant extracts are always merged back in.
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Dynamic rule linkage
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Spatial map values
1974 to current year.
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