Directory chainstate
The
chainstate directory is a
LevelDB database and managed by
CDBWrapper.
It represents all currently unspent
transactions along with some information where these transactions come from.
Using this database speeds up validation of
transactions. Without this database, such a validation would also be possible, but the
entire block-data would have to be scanned for
every output being spent.
The data could be rebuilt from the block data which. However, that takes a long time. (See -reindex command line flag).
CCoinsView backed by the coin database (chainstate)
Testnet
If bitcoin-qt is run with -testnet, it creates the directory testnet3 under the data diretory.
testnet3 then contains the same files (with different content) as the data directory.