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Memory Threshold Notifications

Table Of Contents

Memory Threshold Notifications

Contents

Information About Memory Threshold Notifications

Memory Threshold Notifications

Memory Reservation

How to Define Memory Threshold Notifications

Setting a Low Free Memory Threshold

Reserving Memory for Critical Notifications

Configuration Examples for Memory Threshold Notifications

Setting a Low Free Memory Threshold: Examples

Reserving Memory for Critical Notifications: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for Memory Threshold Notifications


Memory Threshold Notifications


First Published: August 21, 2003
Last Updated: May 2, 2008

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 Support Information for Platforms and Cisco IOS Software Images

Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.

Contents

Information About Memory Threshold Notifications

How to Define Memory Threshold Notifications

Configuration Examples for Memory Threshold Notifications

Additional References

Feature Information for Memory Threshold Notifications

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

Memory Reservation

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

This section contains the following procedures:

Setting a Low Free Memory Threshold

Reserving Memory for Critical Notifications

Setting a Low Free Memory Threshold

To set a low free memory threshold, perform the following steps:

SUMMARY STEPS

1. enable

2. configure terminal

3. memory free low-watermark {processor threshold | io threshold}

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

memory free low-watermark processor threshold

or

memory free low-watermark io threshold

Example:

Router(config)# memory free low-watermark processor 20000

or

Example:

Router(config)# memory free low-watermark io 20000

Specifies a threshold in kilobytes of free processor or input/output (I/O) memory. To view acceptable values for the memory threshold, enter the following command:

memory free low-watermark processor ?

or

memory free low-watermark io ?

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:

SUMMARY STEPS

1. enable

2. configure terminal

3. memory reserve critical kilobytes

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

memory reserve critical kilobytes

Example:

Router(config)# memory reserve critical 1000

Reserves the specified amount of memory in kilobytes so that the router can issue critical notifications.

The amount of memory reserved for critical notifications cannot exceed 25 percent of total available memory.

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

Reserving Memory for Critical Notifications: Example

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:

http://www.cisco.com/go/mibs


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.

http://www.cisco.com/techsupport


Feature Information for Memory Threshold Notifications

Table 1 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.


Note Table 1 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.


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.