Oracle7 Server Distributed Systems Volume II: Replicated Data
SNP Background Processes
Background processes, called SNP background processes, execute job queues.
SNP processes periodically wake up and execute any queued jobs that are due to be run. You must have at least one SNP process running to execute your queued jobs in the background.
SNP background processes differ from other Oracle background processes in that the failure of an SNP process does not cause the instance to fail. If an SNP process fails, Oracle restarts it.
Multiple SNP Processes
An instance can have up to thirty-six SNP processes, named SNP0 to SNP9 and SNPA to SNPZ. If an instance has multiple SNP processes, the task of executing queued jobs can be shared across these processes, thus improving performance. Note, however, that each job is run at any point in time by only one process. A single job cannot be shared simultaneously by multiple SNP processes.
Starting Up SNP Processes
The job queue initialization parameters allow you to control the operation of the SNP background processes. Set these parameters in the initialization parameter file for an instance. They take effect the next time you start the instance.
Table 10 - 1 describes the job queue initialization parameters.
| Parameter Name
| Description
|
|
| JOB_QUEUE_PROCESSES
| Default:
| 0
|
|
| Range of values:
| 0...36
|
|
| Multiple instances:
| can have different values
|
|
| Sets the number of SNP background processes per instance.
|
|
| JOB_QUEUE_INTERVAL
| Default:
| 60 (seconds)
|
|
| Range of values:
| 1...3600 (seconds)
|
|
| Multiple instances:
| can have different values
|
|
| Sets the interval between wake-ups for the SNP background processes of the instance.
|
|
Table 10 - 1. Job Queue Initialization Parameters