Swap Space Bottleneck During SAP Operation (SAP Library - SAP Memory Management (BC-CST-MM))

Swap Space Bottleneck During SAP Operation

Symptom

Diverse error messages that refer to memory bottlenecks, or, more precisely, a swap space bottleneck. For example, System Panic; cmemreserve: reservation overrun; ENOMEM, Not enough core; ENOSPC, No space left on device; SIGDANGER (under AIX only). In the SAP System, the SAP system log message "no memory of class perm" is output.

This problem can occur with SAP processes and external processes as well. The relevant process cannot allocate anymore heap memory. This can lead to the database operation being ended or SAP work processes being stopped.

Error messages in the SAP System appear in the developer trace files dev_disp, dev_w<n> in the system log and in dumps. The following messages may appear: TSV_TNEW_;._NO_ROLL_MEMORY; NO_MEM; NO_MEMORY; RESIZE_EM_ALLOC_ERROR, Storage class PERM.

This problem mostly occurs if background jobs are active with large amounts of data.

Possible Causes

There is no more swap space available (Swap Space Requirements).

The highest value for one of the SAP profile parameters that limit the swap space usage has been exceeded. In this case, the following parameters are relevant: abap/heap_area_dia, abap/heap_area_nondia and abap/heap_area_total.

The operating system limits for the process size (segment size) have been exceeded. For example, no more that 256 MB can be assigned under AIX and no more than 384 under SINIX.

Corrective action

Increase the swap space or decrease the SAP Extended Memory. If the swap space already corresponds to the SAP recommendations, 1.5 to 2 GB may still be required. There should always be several hundred MB of free swap space available. You can reduce the maximum swap space need of the SAP System by reducing the value of parameter abap_heap_area_total. For more detailed information, see Monitoring the Memory Management System.

You can also distribute the load onto several application servers and increase the roll area. Check if the maximum process size (operating system parameters) is sufficient.

This graphic is explained in the accompanying text

Other problems relating to swap space are described in the platform-dependent section.