a disk block is time consuming because of the seek time s and rotational delay (latency) rd.

Double buffering can be used to speed up the transfer of contiguous disk blocks.

Type of records:

Records contain tracks which have values of a particular type

Variable length fields can be mixed into one record

Refers to storing a number of records in one block on the disk

There may be empty space in a block if an integral number of records do not fit in one block.

bfr refers to the number of records per disk.

Refers to records that exceed the size of one or more blocks and hence span a number of blocks.

is a sequence of records

includes information that describes the file

Blocking factor is the (average) number of file records stored in a disk block.

A file can have fixed-length records or variable-length records.

File records can not be unspanned or spanned

no record can span two blocks

Spanned: a record can be stored in more than one block

ordered Files called a heap or a pile file.

ordered Files called:

New records are inserted at the end of the file in Unordered Files

Record insertion is quite efficient in Ordered Files .

Reading the records in order of a particular field requires sorting the file records