• Handler_prepare 

A counter for the prepare phase of two-phase commit operations. 

• Handler_read_first 

The number of times the first entry in an index was read. If this value is high, it suggests that the server is doing a lot of full index scans (for example, SELECT col1 FROM foo , assuming that col1  is indexed). 

• Handler_read_key 

The number of requests to read a row based on a key. If this value is high, it is a good indication that your tables are properly indexed for your queries. 

• Handler_read_last 

The number of requests to read the last key in an index. With ORDER BY , the server issues a first-key request followed by several next-key requests, whereas with ORDER BY DESC , the server issues a last- key request followed by several previous-key requests. 

• Handler_read_next 

The number of requests to read the next row in key order. This value is incremented if you are querying an index column with a range constraint or if you are doing an index scan. 

• Handler_read_prev 

The number of requests to read the previous row in key order. This read method is mainly used to optimize ORDER BY ... DESC . 

• Handler_read_rnd 

The number of requests to read a row based on a fixed position. This value is high if you are doing a lot of queries that require sorting of the result. You probably have a lot of queries that require MySQL to scan entire tables or you have joins that do not use keys properly. 

• Handler_read_rnd_next 

The number of requests to read the next row in the data file. This value is high if you are doing a lot of table scans. Generally this suggests that your tables are not properly indexed or that your queries are not written to take advantage of the indexes you have. 

• Handler_rollback 

The number of requests for a storage engine to perform a rollback operation. 

• Handler_savepoint 

The number of requests for a storage engine to place a savepoint. 

• Handler_savepoint_rollback 

The number of requests for a storage engine to roll back to a savepoint. 

• Handler_update 

The number of requests to update a row in a table. 

• Handler_write 

