Understanding Caching

Caching is a process that stores a local copy of frequently accessed content of remote objects. Caching can improve performance. JD Edwards EnterpriseOne software caches information in these ways:

• The system automatically caches some tables, such as those associated with constants, when it reads them from the database at startup.

  It caches these tables to a user's workstation or to a server for faster data access and retrieval.

• Individual applications can be enabled to use cache.

  JDECACHE APIs enable the server or workstation memory to be used as temporary storage.

JDECACHE is a component of JDEKRNL that can hold any type of indexed data that the application needs to store in memory, regardless of the platform on which the application is running; therefore, an entire table can be read from a database and stored in memory. No limitations exist regarding the type of data, size of data, or number of data caches that an application can have, other than the limitations of the computer on which it is running. Both fixed-length and variable-length records are supported. To use JDECACHE on any supported platform, you need to know only a simple set of API calls.

Data handled by JDECACHE is in RAM. Therefore, ensure that you really need to use JDECACHE. If you use JDECACHE, design the records and indices carefully. Minimize the number of records that you store in JDECACHE because JD Edwards EnterpriseOne software and various other applications need this memory as well.

JDECACHE supports multiple cursors, multiple indexes, and partial keys processing. JDECACHE is flexible in terms of positioning within the cache for data manipulation, which improves performance by reducing searching within the cache.

The JDB environment creates, manages, and destroys the JDECACHE environment. Each cache that you use within the JDECACHE environment is associated with a JDB user. Therefore, you must call JDB_InitBhvr API before you call any of the JDECACHE APIs.