Swap Space Requirements 
SAP application servers are important users of swap space. If the swap space on a computer is used up, serious system problems occur as a result.
Recommendation
For optimal performance SAP recommends the following swap space:
20 GB on 64 bit systems
3-6 GB on 32 bit Linux
Why?
64-bit technology means that the address space can now be used more generously. This minimizes maintenance requirements and the problems associated with memory management, since the size of the buffers and other areas in the shared memory can be increased considerably so that programs do not reach the system limits.
As a result, there is no risk of program crashes due to memory bottlenecks and no need for complex “parameter tuning”.
Note
Large parameter values and address spaces do not automatically mean more main memory is required. The main memory required is determined by the extent to which the configured areas are actually used.
Expanding the swap space may require additional disk space in certain circumstances. This is highly recommended due to inexpensive hardware prices.
The additional swap space requirements may be higher for application servers where heavy online operations and background jobs with large data volumes alternate (day/night operation).
Independent of the swap space size, you should monitor the swap space itself to avoid bottlenecks.
Monitoring Swap Space Usage
To monitor swap space, you can use either the monitoring tool for host operating systems or the system monitor from the SAP Computing Center Management System (CCMS). The CCMS Alert Monitor, which is available via the system monitor, issues warning messages if the swap space usage exceeds a preset limit. You can also display the present usage.