Media database: Index component

Index blocks contain 10 bytes of control information followed by a maximum of 255 items, or keys, each of which has a variable length.

The key length (key_len) of the Media Index file is 49. This value must not be changed.

The default block size (blk_size) of the Media Database index component is 3,174. If you want to change the block size, you can employ any value. BMC recommends that you use a value that will minimize wasted space on the device to which the Index file is allocated.

The required number of blocks (num_blks) is calculated as follows:

num_blks = 1.05 * y

where y is calculated by the following steps:

1. y1 is the number of records in the data component of the Media Database (num_rcds)
   For information on calculating num_rcds, see Media database: Data component.
2. y2 is the number of volumes at the site (x2 in the data component calculations)
3. y3 is the number of data sets at the site multiplied by 2
   This number (y3) can be calculated according to the formula
   y3 = x2 * x3 * 2
   where:
   • x2 is the number of volumes at the site
   • x3 is the average number of files on each volume

   Use the same values for x2 and x3 that you used in calculating the data component (as described in Media database: Data component)

4. y4 is 10% of y1, that is, y1 / 10
   It is assumed that 10% of the records in the data component of the Media Database are other records.
5. y5 is y2 + y3 + y4
6. y6 is y5 * (key_len + 6)
7. y is (y6 / blk_size) * 2