Hi,
Its a memory issue, so you need to optimize the code like where some select statements are there ,
check those statements and put a select only on required fields, use where clause.
2. Check if some select statement is written in loop, it should be taken out of the loop and make use of internal table.
This will solve your problem.
Otherwsie BASIS team needs to be contacted to extend the table space at DB level, but first code should be checked for optimization.
Hope thsi helps.
Thanks