Using an XAE Type 2 Database

If you use an XAE Type 2 database to store AutoEdit variables, the variables are stored both in the Common Service Area (CSA) and using the Coupling facility.

Resolving variables, regardless of from which machine, is always more expensive than with XES Type 1. This is because

• In the best case scenario, the system checks a directory-only caching mechanism implemented with a lock or cache XES structure pair to know if the ECSA copy of the variable is still valid.
• In the worst case scenario, the system must both record your interest in that variable, read the Coupling facility for the latest copy and keep that copy in ECSA).

Setting variables, regardless of from which machine, is always more costly than with XES Type 1. This is because, in addition to updating the ECSA, the system

• updates a directory-only caching mechanism implemented with a lock or cache XES structure pair, to invalidate the ECSA values stored in other computers
• updates the Coupling facility

Serializing the usage of XAE Type 2 database variables requires that you obtain both per-CPU latches and Sysplex-wide locks that can suspend and delay the execution of an address space. Make sure to avoid the excessive delay of important system address spaces.