A keyed file is made up of data and tables. Data and tables have the same size, and each block contains the following control information:
Word 0
Contains the following information about the block, table organization, and key size:
|
Field |
Value |
Meaning |
|---|---|---|
|
[47:04] |
|
Type of block |
|
|
1 |
Coarse table |
|
|
2 |
Fine table |
|
|
3 |
Data block |
|
[43:01] |
Table organization (coarse and fine tables) |
|
|
|
0 |
Descending order by key |
|
|
1 |
Ascending order by key |
|
[15:16] |
|
Size of each key entry (coarse and fine tables) |
Word 1
Contains the following information about the keys for coarse and fine tables:
|
Field |
Meaning |
|---|---|
|
[47:16] |
First key entry (word offset) |
|
[31:16] |
Number of keys currently in table |
|
[15:16] |
Maximum number of key entries that can fit in the table |
Word 2
Address (relative segment number) of this block.
Word 3
Address (relative segment number) of the next sequential fine table. This word links fine tables together so that the file can be accessed sequentially.
|
Field |
Meaning |
|---|---|
|
[43:24] |
Relative segment number of the first available block |
Word 4
Address (relative segment number) of the previous sequential fine table. This word maintains the sequential ordering of fine tables.
|
Field |
Meaning |
|---|---|
|
[43:24] |
Relative segment number of the first available block |
Word 5
Timestamp of the block. This word is used in recovery.
