Managing an Environment for Subsetting › Minimize Host Encyclopedia Contention

Minimize Host Encyclopedia Contention

Host Encyclopedia contention is competition for database resources. Host Encyclopedia contention has two sources:

• CA Gen contention, which are constraints (rules) built into the CA Gen toolsets
• CA Gen contention occurs only at the model and subset level. All CA Gen constraints involve shared use of a single model. No encyclopedia‑wide contention exists. If one analyst is working on Model A and another is working on Model B, CA Gen constraints create no contention. System constraints for simultaneous execution appear in the Subset Concurrency Matrix.

Here the concurrency means:

• A second process can access the Host Encyclopedia without being queued by a process that is already executing.
• The beginning of one process does not depend on the completion of another.
• The first process is not one that locks the entire encyclopedia during its execution.

When system contention occurs, the second process that is submitted to the Host Encyclopedia receives a message that it has been queued. That is, the second process is on hold awaiting resources that are held by the first process. The second process continues to try to determine whether the queue still applies. After ten retries, the attempt to execute the second process terminates with a resource conflict message.