Normally truncation would be caused by setting the length of the variable too short. You should just make the length longer than you expect to see. The maximum a character variable can hold is 32767 bytes.
Transcoding can also change the width. So if you are running UTF-8 and reading something that non 7-bit ASCII codes then single byte codes might get stored in your SAS variables in 2, 3 or 4 bytes. So again make sure the character variable is longer than it needs to be.
Also too short of a LRECL setting on the INFILE statement can cause truncation. You should be able to see this in the notes that SAS writes at the end of the data step. The LRECL maximum depends on your environment but can usually be over one million bytes if you need it to be.
FORMATS as someone mentioned can make values appear to be truncated. If you model code after the messy code that PROC IMPORT generates then you will end up attaching FORMATS and INFORMATS to many variables that do not need them. Instead of using the INFORMAT statement as if it was intended to define a variable use the LENGTH or ATTRIB statements that are intended to define a variable.
The final issue that can cause a lot of trouble is embedded end of line characters in the middle of a value. This is very likely to happen with NOTE fields since people will tend to put in paragraphs of information. If you are lucky your actual end of lines are marked iwth CRLF and any embedded line breaks in the NOTE field use just one of the other. In that case try using the TERMSTR=CRLF option on the INFILE statement. If this does not solve the issue there are a number of topics on this forum of users with this question and ways to pre-process the file to eliminate the embedded line breaks.
Here is the format I like to use for a data step to read a CSV or other delimited file. (1) Define the variables using a LENGTH statement (2) INFILE statement (3) INFORMAT statement for any variable that NEEDS them. (4) FORMAT statement for any variable that NEEDS them. (5) INPUT statement. If you define the variables in the LENGTH statement in the order that they appear in the source file then the input statement can just use a positional variable list ("input firstvar -- lastvar;"). (6) Any LABEL statements for variables where the name is not clear enough.
data want ;
length id 8 date 8 note $32767 ;
infile 'myfile.csv' dsd firstobs=2 lrecl=1000000 termstr=CRLF truncover ;
informat date mmddyy. ;
format date yymmdd10.;
input id -- note ;
run;
Another source of truncation could be a poorly formed delimited file where a value that contains the delimiter is not properly quoted. If you are lucky and this can only happen on the last field on the line then read that field using formatted input. This will read the delimiters as part of the data.
input id date note $32767.;
If not then there are also many postings on this site about that issue. If there is only one field that could contain the delimiter then it is pretty easy to fix. Otherwise your best solution, if possible, is to request that the file be re-generated using proper quoting of values that contain delimiters (or quotes).
