Deciling is a way of Ranking a list of Data; after grouping them into 10 different groups based on a key value.
A concept of Percentile.

If the key value is available in the database, then we have the TOP..PERCENT method in SELECT SQL which divides the selected rows into 10 groups and fetch the TOP n'th group. But here, the key value has to be calculated in a COBOL program and then sort the list of rows(or array fields) according to the key value and then divide the list or array into 10 group and rank the top group as 1, second as 2 and so on....

Any idea on a keyword similar to SQL TOP..PERCENT method in COBOL? Is there an easier method?