• Datafile pointer 

The size of the data file pointer, in bytes. It is usually 2, 3, 4, or 5 bytes. Most tables manage with 2 bytes, but this cannot be controlled from MySQL yet. For fixed tables, this is a row address. For dynamic tables, this is a byte address. 

• Keyfile pointer 

The size of the index file pointer, in bytes. It is usually 1, 2, or 3 bytes. Most tables manage with 2 bytes, but this is calculated automatically by MySQL. It is always a block address. 

• Max datafile length 

How long the table data file can become, in bytes. 

• Max keyfile length 

How long the table index file can become, in bytes. 

• Recordlength 

How much space each row takes, in bytes. 

The table description  part of the output includes a list of all keys in the table. For each key, myisamchk  displays some low-level information: 

• Key 

This key’s number. This value is shown only for the first column of the key. If this value is missing, the line corresponds to the second or later column of a multiple-column key. For the table shown in the example, there are two table description  lines for the second index. This indicates that it is a multiple-part index with two parts. 

• Start 

Where in the row this portion of the index starts. 

• Len 

How long this portion of the index is. For packed numbers, this should always be the full length of the column. For strings, it may be shorter than the full length of the indexed column, because you can index a prefix of a string column. The total length of a multiple-part key is the sum of the Len  values for all key parts. 

• Index 

Whether a key value can exist multiple times in the index. Possible values are unique  or multip. (multiple). 

• Type 

What data type this portion of the index has. This is a MyISAM  data type with the possible values packed , stripped , or empty . 

• Root 

Address of the root index block. 

• Blocksize 

