MySQL: What does event `/io/table/sql/handler` mean?
From documentation of solorwinds


  .../sql/handler = work has been delegated to a storage engine
  
  examples:
  
  
  io/table/sql/handler = storage engine is processing an I/O request against a table
  lock/table/sql/handler = storage engine is processing a table lock operation
  


Reference


See the MySQL reference manual for more information on Wait Instrument naming (look at the section for "Wait Instrumented Components"):

https://dev.mysql.com/doc/refman/5.6/en/performance-schema-instrument-naming.html