Guideline For System Service Execution Time Ratio - Omron NX701-1620 User Manual

Appendix B
B-1-4 Guideline for System Service Execution Time Ratio
The DB Connection Service is executed as a system service.
When a DB Connection Instruction is executed by a user program, the DB Connection Service
executes the processing as a system service.
The method of executing the system service depends on the CPU Unit model.
 NJ501-20 and NJ101-20
For NJ501-20 and NJ101-20, if sufficient execution time cannot be allocated to the system
services, the DB Connection Instruction may take long execution time. Or, other processing executed
in the system services may take long execution time.
To execute the DB Connection Instructions according to the performance specifications, design the
task so that the system service execution time ratio (CPU usage) meets the following.
CPU Unit model
NJ501-20
NJ101-20
Precautions for Safe Use
The above system service execution time ratio (CPU usage) is just a guideline.
The appropriate value of system service execution time ratio (CPU usage) depends on the
usage of other services executed as a system service.
Before starting actual operation, you must test performance under all foreseeable conditions on
the actual system and make sure that the DB Connection Instructions are executed within the
appropriate execution time.
Precautions for Correct Use
 If the system service execution time ratio is reduced, operation failures or communications
errors may occur when each operation is executed from Sysmac Studio. If an operation
failure or communications error occurs when you execute an operation from Sysmac Studio,
retry the operation after performing the following:
Check the cable connection.

Check the communications settings.

Increase the response monitoring time in the Communications Setup.

Check that the operation status of the DB Connection Service is not Initializing, Error, or

Shutdown.
For details of the operation status of the DB Connection Service, refer to 4-3-1 Operation
Status of the DB Connection Service.
When Sysmac Studio cannot go online, refer to the NJ/NX-series Troubleshooting Manual

(Cat. No. W503) for details.
If the time set for system service monitoring cannot be secured for system services, an

Insufficient System Service Time Error will occur. The error is a major fault level Controller
error. When the error has occurred, user program execution stops. To secure enough time for
system services and task execution, set the minimum value that can satisfy the response
performance of the system service processing for system service monitoring. The system
service monitoring setting is just for monitoring whether or not the specified time can be
secured for system service execution. It does not guarantee that system services are
executed for the specified time.
The system service execution time is affected by task execution time and tag data links. Refer

B-8

Guideline for system service execution time ratio

20% or greater
40% or greater
NJ/NX-series Database Connection CPU Units User's Manual (W527)