question: @ Override public InStore openRead ( long address , int size ) { if ( fileSize ( ) < address + size ) { throw new IllegalStateException ( L . l ( "{0} read open for length {1}:{2} but file length {3}" , this , address , size , fileSize ( ) ) ) ; } if ( _isClosed . get ( ) ) { throw new IllegalStateException ( L . l ( "{0} is closed." , this ) ) ; } if ( _fileSize < address + size ) { throw new IllegalStateException ( L . l ( "Open read of large file {0}:{1}" , Long . toHexString ( address ) , size ) ) ; } try { streamOpen ( address , size ) ; return openReadImpl ( address , size ) ; } catch ( IOException e ) { throw new RuntimeException ( e ) ; } }
target:  Opens the underlying file to the database.