Need help creating optimal Static Hashed File

[gateleys]

I need to create a Static Hashed File that contains the following columns-

Total number of rows = 10,000,000 (10 million)
SomeDateAndTime KEY, TIMESTAMP(19) eg. 2010-05-12 09:30:45
FirstAmount Non-Key, INTEGER(7) eg. 1234567
SecondAmount Non-Key, INTEGER(7) eg. 1234567

I am using the HFC calculator to generate the mkdbfile command for the hashed file creation. My parameters are as follows-

Static Hashed File Type 2
Row size = 19 bytes (key col)+ 7 bytes (first amount) + 7 bytes (second amount)+ 2 bytes (for two delimiters) + 2 bytes (for CRLF) + 14 bytes (for overhead) = 51 bytes
Total number of rows = 10,000,000


Baed on the above, the HFC.exe spits out the following command -

Code: Select all

mkdbfile testStaticHFile 2 1250003 1 -32BIT

I, see that the file thus created is about 640 MB. However, when I populate the file, the size is about 1.1 GB.

1. Am I computing my row size incorrectly?
2. Should I be using some other Type (and not Type 2)?
3. Similar static hashed file with about half the number of rows gave a decent lookup performance. However, with the new file, the performance has been painfully slow. Any ideas?


Thanks

[gateleys]

BTW, I have left the Separation to default of 1.

[ray.wurlod]

Type 2 isn't really that appropriate for timestamp. Try type 18, or perhaps Type 5.

At 51 bytes per record, separation 1 is fine, but separation 2 or 4 may be more efficient because of matching the physical page size used in your hardware.

Finally, try choosing a prime number as the modulo. The hfc.exe program has this as an option.