Oracle C++ Call Interface Programmer's Guide

Developing an OCCI Object Application
reference is dereferenced for the first time and decremented when the reference
goes out of scope. When the pin count of the object becomes 0, indicating that all
references to that object are out of scope, the object is automatically eligible for
garbage collection and subsequently deleted from the cache.
For persistent objects that have been created by calling the new operator, you must
call a delete if you do not commit the transaction. Otherwise, the object is garbage
collected after the commit. This is because when such an object is created using new,
its pin count is initially 0. However, because the object is dirty it remains in the
cache. After a commit, it is no longer dirty and thus garbage collected. Therefore, a
delete is not required.
If a commit is not performed, then you must explicitly call delete to destroy that
object. You can do this as long as there are no references to that object. For transient
objects, you must delete explicitly to destroy the object.
You should not call a delete operator on a persistent object. A persistent object that
is not marked/dirty is freed by the garbage collector when its pin count is 0.
However, for transient objects you must delete explicitly to destroy the object.
Tuning the Object Cache
The object cache has two important associated parameters:
■ The maximum cache size percentage
■ The optimal cache size
These parameters refer to levels of cache memory usage, and they help to determine
when the cache automatically "ages out" eligible objects to free up memory.
If the memory occupied by the objects currently in the cache reaches or exceeds the
maximum cache size, the cache automatically begins to free (or age out) unmarked
objects which have a pin count of zero. The cache continues freeing such objects
until memory usage in the cache reaches the optimal size, or until it runs out of
objects eligible for freeing.
The maximum object cache size (in bytes) is computed by incrementing the optimal
cache size (optimal_size) by the maximum cache size percentage (max_size_
percentage), as follows:
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Note: The cache can grow beyond the specified maximum cache
size.