>>I write a app that recieve serial port data into a table
>>by MSCOMM32.OCX.
>> I use a memo field to save data what recieved , and per record is 100K long about,but when i have recieved 5 records , i find it's become 21M long!!! (the FPT file of this table) I don't know what is happend. or memo field has some fix block for saving data, they are fix long,and whatever they are used ?
>> how can i try ?
>> (If someone is interest it , i can post my code to him via E-Mail..)
>> thanks everyone.
>
>
>Memo fields use a specific block size. When the block is filled, the ENTIRE memo for that field is copied to the end of the FPT file and another block is reserved. The original space is NOT reclaimed. Use PACK MEMO to reclaim the space.
>
>Craig

In addition to what Craig has said, here is the end portion of some tests we did
trying to resolve the same issue.



data table=test
1 memo field name test
1 record in place

Test 4:

REPL TEST WITH ‘‘
PACK
fpt size is 512

for i=1 to 11776
repl test with test+’*’
endf

len(test)=11776
fpt size is 1,101,632

PACK
fpt size is 12,352
Overhead of Replace + command is 1,089,280 in diskspace !!!!!!!

Conclusion:
If this were happening only during program execution, we might assume that a buffering effect
was causing the memo field to grow. Since it also happens in manual, single line execution, we
are going to assume that the replace test+ command is the cause. FoxPro may retain a portion
of the memo field on disk, causing the growth.

Further tests showed that the most conservative use of diskspace is to capture incomming
communications to a variable. When the variable reaches 16K in size, write the data to a
memo field for safety. Continue this pattern until the communication is completed, write the
final variable data to the memo field.

Use replace field+data in memo fields very conservatevly, infrequently.