Databases Reference
In-Depth Information
Figure 5: Object Reference Table and References to Local Objects
Dynamic Performance Optimization Mechanism
The dynamic performance optimization mechanism has been designed as a suite
of dynamic object relocation mechanisms. These relocation strategies are based
on approximate load information, which can be collected without significant
overhead at run time.
The basic strategies are categorized as follows
13)
.
1.
Object count balancing
This strategy relocates objects so that the number of objects on each PE
becomes approximately equal. Object count balancing is quite simple since
this strategy only compares the maximum and minimum numbers of objects
allocated to PEs and relocates surplus objects to the PEs that have fewer
objects.
2.
External reference reduction
If a certain object has a larger external reference frequency, that object is
relocated to the PE that accesses it most frequently.
For each object in each PE, this strategy requires additional storage space
in order to collect the information necessary for determining the relocation
candidates and the relocation destinations.
3.
Locality preference enforcement
If a certain type of reference among objects is known to be accessed
frequently, a pair of objects linked by that special reference should be
allocated on the same PE. This strategy corresponds to object clustering.
