Synchronously checkpoint the database environment.
This is an optional action for the application since this activity is, by default, handled by a database environment owned background thread.
A checkpoint has the side effect of flushing all preceding non-transactional write operations, as well as any preceding transactions that were committed with {@link Durability.SyncPolicy#NO_SYNC no-sync durability}. However, for best performance, checkpoints should be used only to bound recovery time. {@link #flushLog} can be used to write buffered data for durabilitypurposes.
@param ckptConfig The checkpoint attributes. If null, defaultattributes are used.
@throws EnvironmentFailureException if an unexpected, internal orenvironment-wide failure occurs.
@throws IllegalStateException if this handle or the underlyingenvironment has been closed.