The complete error message canappear like this:
%SYS-DFC7-2-MALLOCFAIL: Memory allocation of xxxx bytes failed from 0xYYYYYYYY, alignment x
This problem occurs due to the presence of the Cisco bug ID CSCei20107.
The problem is that two processes start to consume memory once the SPAN session is configured.
This problem is fixed in Cisco IOS Software Releases 12.2(18)SXE4 and Cisco IOS Software Releases 12.2(18)SXF and later.
In order to resolve this problem, upgrade the Cisco IOS Software on the switch to the latest maintenance release, which can be downloaded from Cisco Downloads.
For further assistance and support, use the TAC Service Request Tool in order to open a service request with Cisco Technical Support.
Catalyst 6000 series switches
Catalyst 6500 series switches
Catalyst 6000 modules