Interstage Shunsaku Data Manager Operator's Guide - Microsoft(R) Windows(R) 2000/ Microsoft(R) Windows Server(TM) 2003 - - UNIX -

8.1.3 Degradation Function for Searchers

If errors occur on searchers, operations can be recommenced in minimal time due to the searcher degradation function.
However, using degradation, the amount of data allocated to each searcher operation normally increases, and so the same performance as before degradation cannot be expected. Search data must also be reallocated once the failed searcher is restored.

The following diagram shows the flow of degradation processing for searchers.

[Figure : Flow of Degradation Processing for Searchers]

Controlling Searcher Degradation

Because of the searcher degradation operation, the search performance may be worse than expected, and may cause the operation trouble. Furthermore, unexpected number of fault servers may cause the active searchers memory insufficiency and the degradation operation may not be able to continue.
In preparation for the problem above, set the number of searchers that can be degraded in advance. This will control the system not to degrade searchers more than the setting value when a searcher degradation occurs.
This function is available when the DegradableSearcherCnt Parameter is set in the system environment file or director environment file.

If this function is located in a valid director and the error occurs at the searcher connected with that director, the system will run the following operations.

• If the number of fault searchers is less than the setting value, the system will perform the degradation and recommence the operation.
• If the number of fault searchers is more than the setting value, the degradation will not be performed and the director will change to the [Director waiting for connection to searcher] status.

The merit of these operations is:

• The data in the active searchers is still stored in where it is. Therefore the system can distribute the data in a minimal time after the problem is solved.

For the setting value, design the value according to the search performance and the searcher memory.
For the search performance, when estimate the search performance, assume that the performance become slower in the proportion of the amount of data allocated to searchers during the degradation. For the memory, estimate the memory regarding to the amount of data allocated to searchers during the degradation.

The following diagram shows the approach to controlling searcher degradation.

[Figure : An Approach to Controlling Searcher Degradation]

Note that if the number of fault searchers is more than the setting value, the business operation has to be temporarily stopped.
This function is recommended if the operation has a high priority on the search performance and the business operation can be stopped to recover the system.

Refer to Appendix A Execution Parameters in Environment Files for more information on system environment file or direct environment file.

Refer to Recovering from Searcher Failovers in the Troubleshooting for more information on how to handle the problem when the value of DegradableSearcherCnt parameter has exceeded the setting value.