Class Mapping

All Persistent classes use some kind of storage scheme to define how the properties of the class are mapped to physical on-disk storage. Cache provide three different built-in storage schemes:

Cache Storage

The default storage scheme for persistent Cache classes is implemented by %Library.CacheStorage. It creates a well designed and optimised physical structure with a lot of inherent flexibility and extensibility.

Cache SQL Storage

The Cache SQL Storage Scheme is implemented by %Library.CacheSQLStorage. It provides a way of mapping a class manually to a wide range of physical structures. An SQL projection of the class is generated automatically.

The main use of this storage scheme is to enable ODBC access to native global structures. Occassionally it is used to provide Object access to native global structures but this is less common.

Custom Storage

The Custom Storage Scheme provides a way of writing custom methods for each property and operation in the class. It is implemented using %Library.CustomStorage. Usage is not very common because it does not automatically provide an ODBC interface to the class. This can however be overcomed by inserting the following parameter into the class:

Parameter SQLENABLED = 1;