[EMAIL PROTECTED] wrote on 12/12/2005 11:06:37 PM:
> I'm seeking some advice from others on reasonable parameters for a
> KEYONLY dynamic hashed file on unidata.
The following is swiped from an old technical bulletin and is a good
starting point. You should run guide with the -r option on the file and
use its output for the variables below. However, there's nothing like
getting a small sample of the records in the file - maybe 1 percent, and
creating a small test file to play around with. You can play with
CONFIGURE.FILE and memresize to find the best parameters, then use those,
with an increased modulo to size the real file.
For what it's worth, I generally find that smaller split and load numbers,
such as 20/10, work better than larger ones. Of course, that varies from
file to file, and there is no absolute rule.
=============================================================================
=================
Formula for determining base modulo, block size, SPLIT_LOAD, and
MERGE_LOAD for UniData KEYONLY Dynamic Files
Note that the variables used are the same as the DICT items in
$UDTHOME/sys/D_UDT_GUIDE. Any calculated values which are not attributes
in this dictionary appear in bold italic.
Considerations:
The following does not take into account the Unix disk record
(frame) size so it is best to
select a block size based on the number of items you?d like in a
group.
No one method will provide absolute results but these calculations
will minimize level one
overflow caused by a high SPLIT_LOAD value.
Type 0 works best for most Dynamic Files but it is best to check a
small sample via the
GROUP.STAT command.
Step 1: Determine the blocksize. (Use 4096 unless the Items per
group is larger then 35 or less then 2)
A) If the MAXSIZ < 1K
ITEMSIZE = 10 * MAXSIZ
B) If 1 K < MAXSIZ < 3 K
ITEMSIZE = 5 * MAXSIZ
C) If MAXSIZ > 3 K
ITEMSIZE = 5 * (AVGSIZ + DEVSIZ )
Once you determine the item size, use it to determine the NEWBLOCKSIZE.
A) ITEMSIZE < 1024; NEWBLOCKSIZE = 1024
B) 1024 > ITEMSIZE < 2048; NEWBLOCKSIZE = 2048
C) 2048 > ITEMSIZE < 4096; NEWBLOCKSIZE = 4096
D) 4096 > ITEMSIZE < 8192; NEWBLOCKSIZE = 8192
8192 > ITEMSIZE < 16384; NEWBLOCKSIZE = 16384
Step 2: Determine the actual number of items per group.
ITEMS_PER_GROUP = NEWBLOCKSIZE-32 / AVGSIZ
Step 3: Determine the base modulo
BASEMODULO = COUNT / ITEMS_PER_GROUP
Step 4: Determine SPLIT_LOAD
SPLIT_LOAD=INT((((AVGKEY + 9) * ITEMS_PER_GROUP ) / NEW_BLOCKSIZE)*100)+1
If the SPLIT_LOAD is less then ten then: SPLIT_LOAD = 10
Step 5: Determine MERGE_LOAD
MERGE_LOAD = SPLIT_LOAD / 2 ( Rounded up )
Tim Snyder
Consulting I/T Specialist , U2 Professional Services
North American Lab Services
DB2 Information Management, IBM Software Group
717-545-6403
[EMAIL PROTECTED]
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