Memory Threshold Notifications
The Memory Threshold Notifications feature allows you to reserve memory for critical notifications and to configure a router to issue notifications when available memory falls below a specified threshold.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Information About Memory Threshold Notifications
The Memory Threshold Notifications feature provides two ways to mitigate low-memory conditions on a router: notifications can be sent to indicate that free memory has fallen below a configured threshold, and memory can be reserved to ensure that sufficient memory is available to issue critical notifications. To implement the Memory Threshold Notifications feature, you should understand the following concepts:
Memory Threshold Notifications
Notifications are messages issued by the router. When you specify a memory threshold using the memory free low-watermark command, for example, the router issues a notification when available free memory falls below the specified threshold, and again once available free memory rises to 5 percent above the specified threshold. The following are examples of memory threshold notifications:
Available Free Memory Less Than the Specified Threshold
000029: *Aug 12 22:31:19.559: %SYS-4-FREEMEMLOW: Free Memory has dropped below 2000k Pool: Processor Free: 66814056 freemem_lwm: 204800000
Available Free Memory Recovered to More Than the Specified Threshold
000032: *Aug 12 22:33:29.411: %SYS-5-FREEMEMRECOVER: Free Memory has recovered 2000k Pool: Processor Free: 66813960 freemem_lwm: 0
Memory Reservation
Memory reservation for critical operations ensures that management processes, such as event logging, continue to function even when router memory is exhausted.
How to Define Memory Threshold Notifications
Setting a Low Free Memory Threshold
To set a low free memory threshold, perform the following steps:
- memory free low-watermark processor threshold
- memory free low-watermark io threshold
DETAILED STEPS
Reserving Memory for Critical Notifications
When a router is overloaded by processes, the amount of available memory might fall to levels insufficient for it to issue critical notifications. To reserve a region of memory to be used by the router for the issuing of critical notifications, perform the following steps:
DETAILED STEPS
Configuration Examples for Memory Threshold Notifications
The following examples show how to configure a router to issue notifications when available memory falls below a specified threshold and how to reserve memory for critical notifications:
Setting a Low Free Memory Threshold Examples
The following example specifies a threshold of 20000 KB of free processor memory before the router issues notifications:
Threshold for Free Processor Memory
Router(config)# memory free low-watermark processor 20000
The following example specifies a threshold of 20000 KB of free I/O memory before the router issues notifications:
Threshold for Free IO Memory
Router(config)# memory free low-watermark io 20000
If available free memory falls below the specified threshold, the router sends a notification message like this one:
000029: *Aug 12 22:31:19.559: %SYS-4-FREEMEMLOW: Free Memory has dropped below 20000k Pool: Processor Free: 66814056 freemem_lwm: 204800000
Once available free memory rises to above 5 percent of the threshold, another notification message like this is sent:
000032: *Aug 12 22:33:29.411: %SYS-5-FREEMEMRECOVER: Free Memory has recovered 20000k Pool: Processor Free: 66813960 freemem_lwm: 0
Reserving Memory for Critical Notifications Example
The following example reserves 1000 KB of memory for critical notifications:
Router# memory reserved critical 1000
 Note |
The amount of memory reserved for critical notifications cannot exceed 25 percent of total available memory. |
Additional References
The following sections provide references related to the Memory Threshold Notifications feature:
Related Documents
| Related Topic |
Document Title |
|---|---|
| Logging system messages |
Troubleshooting and Fault Management module |
Standards
| Standards |
Title |
|---|---|
| No new or modified standards are supported by this feature and support for existing standards has not been modified by this feature. |
-- |
MIBs
| MIBs |
MIBs Link |
|---|---|
| No new or modified MIBs are supported by this feature and support for existing MIBs has not been modified by this feature. |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs
| RFCs |
Title |
|---|---|
| No new or modified RFCs are supported by this feature and support for existing RFCs has not been modified by this feature. |
-- |
Technical Assistance
| Description |
Link |
|---|---|
| The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies. To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds. Access to most tools on the Cisco Support website requires a Cisco.com user ID and password. |
Feature Information for Memory Threshold Notifications
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
| Table 1 | Feature Information for Memory Threshold Notifications |
| Feature Name |
Releases |
Feature Information |
|---|---|---|
| Memory Threshold Notifications |
12.2(18)S 12.0(26)S 12.3(4)T |
The Memory Threshold Notifications feature allows you to reserve memory for critical notifications and to configure a router to issue notifications when available memory falls below a specified threshold. |
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
Feedback