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Cisco IOS Software Releases 12.3 T

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

Command Reference

memory free low-watermark

memory reserve critical


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.

Release
Modification

12.2(18)S

This feature was introduced.

12.0(26)S

This feature was integrated into Cisco IOS Release 12.0(26) S.

12.3(4)T

This feature was integrated into Cisco IOS Release 12.3(4)T.


Feature History for the Memory Threshold Notifications Feature

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

Command Reference

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, Logging, and Fault Management" chapter in the Cisco IOS Configuration Fundamentals Configuration Guide


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

Technical Assistance Center (TAC) home page, containing 30,000 pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

http://www.cisco.com/public/support/tac/home.shtml


Command Reference

This section documents new commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 and 12.3T command reference publications.

memory free low-watermark

memory reserve critical

memory free low-watermark

To configure a router to issue notifications when available memory falls below a specified threshold, use the memory free low-watermark command in global configuration mode. To disable memory threshold notifications, use the no form of this command.

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

no memory free low-watermark

Syntax Description

processor threshold

Sets the processor memory threshold in kilobytes. When available processor memory falls below this threshold, a notification message is triggered. Valid values are 1 to 4294967295.

io threshold

Sets the input/output (I/O) memory threshold in kilobytes. When available I/O memory falls below this threshold, a notification message is triggered. Valid values are 1 to 4294967295.


Defaults

Memory threshold notifications are disabled.

Command Modes

Global configuration

Command History

Release
Modification

12.2(18)S

This command was introduced.

12.0(26)S

This command was integrated into Cisco IOS Release 12.0(26)S.

12.3(4)T

This command was integrated into Cisco IOS Release 12.3(4)T


Usage Guidelines

Using this command, you can configure a router to issue a notification each time available free memory falls below a specified threshold ("low-watermark"). Once available free memory rises to 5 percent above the threshold, another notification message is sent.

Examples

The following example specifies a free processor memory notification threshold of 20000 KB:

Router(config)# memory free low-watermark processor 200000

If available free processor memory falls below this 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 processor memory rises to a point 5 percent above 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

Related Commands

Command
Description

memory reserve critical

Reserves memory for use by critical processes.


memory reserve critical

To configure the size of the memory region to be used for critical notifications, use the memory reserve critical command in global configuration mode. To disable the reservation of memory for critical notifications, use the no form of this command.

memory reserve critical kilobytes

no memory reserve critical

Syntax Description

kilobytes

Specifies the amount of memory to be reserved in kilobytes. Valid values are 1 to 4294967295, but the value you specify cannot exceed 25 percent of total memory.


Defaults

kilobytes: 100

Command Modes

Global configuration

Command History

Release
Modification

12.2(18)S

This command was introduced.

12.0(26)S

This command was integrated into Cisco IOS Release 12.0(26)S.

12.3(4)T

This command was integrated into Cisco IOS Release 12.3(4)T


Usage Guidelines

This command reserves a region of memory on the router so that, when system resources are overloaded, the router retains enough memory to issue critical notifications.


Note Once the size of the reserved memory region is specified, any change to the specified value takes effect only after the current configuration is saved and the system has been reloaded.


Examples

The following example shows how to set the size of the memory region to 1000 KB:

Router(config)# memory reserve critical 1000

Related Commands

Command
Description

memory free low-watermark

Configures a router to issue notifications when available memory falls below a specified threshold.