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times of the current sample statement and new statement and, optionally, the age of the current sample statement: 

•Resampling based on wait times: If the new statement wait time has a wait time greater than that of the current sample statement, it becomes the current sample statement. 

•Resampling based on age: If the performance_schema_max_digest_sample_age  system variable has a value greater than zero and the current sample statement is more than that many seconds old, the current statement is considered “too old”  and the new statement replaces it. This occurs even if the new statement wait time is less than that of the current sample statement. 

For information about statement sampling, see Section 27.10, “Performance Schema Statement Digests and Sampling” . 

• performance_schema_max_file_classes 

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The maximum number of file instruments. For information about how to set and use this variable, see Section 27.7, “Performance Schema Status Monitoring” . 

• performance_schema_max_file_handles 

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The maximum number of opened file objects. For information about how to set and use this variable, see Section 27.7, “Performance Schema Status Monitoring” . 

The value of performance_schema_max_file_handles  should be greater than the value of open_files_limit : open_files_limit  affects the maximum number of open file handles the server can support and performance_schema_max_file_handles  affects how many of these file handles can be instrumented. 

