Hashed table is useful when your have to work with very big internal table and to read it with 
"READ TABLE WITH KEY ..." 

The time access is constant ! 

Definition of a Hashed Table: 
"Defines the table as one that is managed with an internal hash procedure. You can imagine a hashed table as a set, whose elements you can address using their unique key. Unlike standard and sorted tables, you cannot access hash tables using an index. All entries in the table must have a unique key. 

Access time using the key is constant, regardless of the number of table entries. 

You can only access a hashed table using the generic key operations or other generic operations (SORT, LOOP, and so on). Explicit or implicit index operations (such as LOOP ... FROM to INSERT itab within a LOOP) are not allowed." 

As long as your records has unique key(s), using hash table will give you a huge performance gain when dealing with large dataset. assuming in your case, 10000 record , and if the key is unique, use hash table.  The main use of hash tables is for looking up fixed information from a key. So if you have a report that has personnel number and you want to display their name, you could use a hash table. 

Thus: 
Code: 

types: begin of typ_pernr, 
         pernr  like pa0001-pernr, 
         ename  like pa0001-ename, 
       end   of typ_pernr. 
data: ls_pernr  type typ_pernr, 
      lt_pernr  type  hashed table of typ_pernr  with unique key pernr. 
... 
  select pernr ename into table lt_pernr  from pa0001. 
... 
  loop at itab. 
    read table lt_pernr  with table key pernr  =  itab-pernr 
         into ls_pernr. 
    write: ls_pernr-ename, itab-data. 
  endloop. 

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