Summary information |
|
|---|---|
Default value |
1 |
Range of values |
1 – 1024 (threaded mode) 1 – 128 (process mode) |
Status |
Static |
Display level |
Intermediate |
Required role |
System administrator |
Configuration groups |
Memory Use, Processors |
max online engines places an upper limit of the number of engine threads that can be brought online. It does not take into account the number of CPUs available at start-up, and allows users to add CPUs at a later date. See Chapter 5, Managing Mulitprocessor Servers,” in System Administration Guide: Volume 2 for a detailed discussion of how to set this parameter for your SMP environment.
At start-up, Adaptive Server starts with a single engine thread and completes its initialization, including recovery of all databases. Its final task is to allocate additional server engines. Each engine accesses common data structures in shared memory.
When tuning the max engines online parameter:
Never have more engine threads online than there are CPUs.
max engines online must be large enough to allow Adaptive Server to bring all the engine thread pools online simultaneously.
Depending on overall system load (including applications other than Adaptive Server), you may achieve optimal throughput by leaving some CPUs free to run non-Adaptive Server processes.
You can achieve better throughput by running fewer engine threads with high CPU use, rather than by running more engine threads with low CPU use.
Scalability is application-dependent. Conduct extensive benchmarks on your application to determine the best configuration of online engine threads.
In process mode, use sp_engine to take engine threads offline or to bring them online. You can take all engine threads offline except engine zero.
See Chapter 3, “Using Engines and CPUs” in the Performance and Tuning Series: Basics .
