Root Cause:
IPDR process gets the report from LC. In normal situations, IPDR use buffer from reserved buffer to send report to collector. When network has dropped pkts and lot of re-transmission, IPDR may need to allocate new buffer. When allocating new buffer, IPDR checks for available free mem. If it is < 35% then it prints the above error and drops the report. In customer situation this issue is seen only on couple of days. Currently IPDR reports are sent with no issues even free mem is < 35%.  So conclusion is whenever this error logged, IPDR report is dropped and functions normally from the next interval if no additional buffer allocation is required. Not a major issue.

Symptom:
%UBR10000-3-IPDR_BUFFER_ERR: unable to alloc buffer 
reported

Conditions:
When network has dropped pkts and lot of re-transmission, IPDR may need to allocate new buffer. When allocating new buffer, IPDR checks for available free mem. If it is < 35% then it prints the above error and drops the report.