kdxconro: number of index entries (does not include kdxbrlmc pointer)
kdxcofbo: offset to beginning of free space within block
kdxcofeo: offset to the end of free space (i.e.. first portion of block containing index data)
kdxcoavs: available space in block (effectively area between kdxcofbo and kdxcofeo)
分支块专用头信息 kdxbrlmc: block address if index value is less than the first (row#0) value（例如在root块中,明明有两条记录，却只包含一个row，这是因为第一个可以通过dkxbrlmc来确定）
kdxbrsno: last index entry to be modified
kdxbrbksz: size of usable block space
叶子块专有头信息 kdxlespl: bytes of uncommitted data at time of block split that have been cleaned out
kdxlende: number of deleted entries
kdxlenxt: pointer to the next leaf block in the index structure via corresponding rba
kdxleprv: pointer to the previous leaf block in the index structure via corresponding rba
Kdxledsz: deleted space
kdxlebksz: usable block space (by default less than branch due to the additional ITL entry)
记录区域： branch entity Row number (starting at #0) followed by [starting location in block] followed by the dba
Column number (starting at 0) followed by column length followed by column value
Repeated for each indexed column
Repeated for each branch entry
leaf entity （unique） Row number (starting at #0) followed by [starting location within block]
followed by various flags (deletion flag, locking information etc.) followed by
total length of index entry followed by the rowid
Index column number (starting at 0) followed by column length followed by
column value
Repeated for each indexed column
Repeated for each index entry
Note: Total overhead is 3 bytes for each leaf index entry (unique index)
leaf entity（ununique） Row number (starting at 0) followed by [starting location within block] followed by various
flags (deletion flag, etc locking information) followed by length of index entry
Index column number (starting at 0) followed by column length followed by column value
Repeated for each indexed column with last column in non-unique index being the rowid of
index entry (hence making the index entry effectively unique anyways)
Repeated for each index entry
Note: Total overhead is 4 bytes, 1 more than unique index