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Monitoring and Maintaining Memory Scan
Memory Scan
This feature module describes the Memory Scan feature. This document contains the following sections:
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Monitoring and Maintaining Memory Scan
Feature Overview
The Memory Scan feature adds a low-priority background process that searches all installed dynamic random-access memory (DRAM) for possible parity errors. If errors are found in memory areas that are not in use, this feature attempts to scrub (remove) the errors. The time to complete one memory scan and scrub cycle can range from 10 minutes to several hours, depending on the amount of installed memory. The impact of the Memory Scan feature on the central processing unit (CPU) is minimal. The feature can be controlled and monitored with the new memory scan and show memory scan command-line interface (CLI) commands.
Benefits
The Memory Scan feature does not discriminate against different information types in DRAM; that is, it perceives text, data, and heap information in the same way. The feature continues to work when a memory cell is busy, although it might respond differently to errors found in different areas. The feature responds to errors in one or more of the following ways:
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Restrictions
The Memory Scan feature is only supported on the Route Switch Processor (RSP) module in Cisco 7500 series routers.
Supported Platforms
This feature is supported on Cisco 7500 series routers.
Prerequisites
Before you configure the Memory Scan feature, you must have a software image that supports the Memory Scan feature on your router. For more information on downloading a software image, refer to the "Loading and Maintaining System Images and Microcode" chapter of the Configuration Fundamentals Configuration Guide, and the "System Image and Microcode Commands" chapter of the Configuration Fundamentals Command Reference publication.
Supported MIBs and RFC
None
List of Terms and Acronyms
dynamic random-access memory (DRAM)— RAM that stores information in capacitors that must be periodically refreshed.
heap—Area of memory used for dynamic memory allocation where blocks of memory are allocated and freed in an arbitrary order.
parity—Extra bit added to a byte or a word to reveal errors in storage (in RAM or disk) or transmission. Even parity means that the parity bit is set so that there are an even number of one bits in the word, including the parity bit. A single parity bit can only reveal single bit errors.
parity errors—Parity errors indicate that internal hardware error checks have failed.
Route Processor (RP)—Processor module in Cisco 7000 series routers that contains the CPU, system software, and most of the memory components that are used in the router. Sometimes called a supervisory processor.
Route/Switch Processor (RSP)—Processor module in Cisco 7500 series routers that integrates the functions of the RP and the SP.
scrub—Function that removes transient parity errors from system memory.
Switch Processor (SP)—Cisco 7000 series processor module that acts as the administrator for all CxBus activities. Sometimes called CiscoBus controller.
Configuration Tasks
Perform these tasks to configure memory scan and verify its operation:
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Configuring Memory Scan
The following table describes the CLI commands used to configure this feature
Router(config)# memory scan
Enables the Memory Scan feature on Cisco 7500 series routers
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Verifying Memory Scan
Use the show running-configuration command in privileged EXEC mode to verify that memory scan appears in the running configuration.
Use the show memory scan command to monitor the number and type of parity errors on your system. Use the show memory scan command in privileged EXEC mode. In the following example, no parity errors are found:
Router# show memory scanMemory scan is on.No parity error has been detected.If memory scan has not been configured or has been turned off, the show memory scan command generates a report. In the following example, memory scan is turned off:
Router# show memory scanMemory scan is offNo parity error has been detected.If errors are detected in the system, the show memory scan command generates an error report containing the following fields:
In the following example, memory scan detected a parity error:
Router# show memory scanMemory scan is on.Total Parity Errors 1.Address BlockPtr BlckSize Disposit Region Timestamp6115ABCD 60D5D090 9517A4 Scrubed Local 16:57:09 UTC Thu Mar 18Monitoring and Maintaining Memory Scan
Router# show memory scan
Monitors the number and type of parity errors on your system.
Configuration Examples
Use the memory scan command to configure the Memory Scan feature on a Cisco 7500 series router. Use the following command in global configuration mode:
Router(config)# memory scanCommand Reference
This section documents new or modified commands.
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memory scan
To enable the Memory Scan feature on a Cisco 7500 series router, use the memory scan command. Use the no form of this command to restore the router configuration to the default.
memory scan
no memory scan
Defaults
This command is disabled by default.
Command Modes
Global configuration
Command History
Example
The following example configures the Memory Scan feature on a Cisco 7500 series router:
Router(config)# memory scanshow memory scan
To monitor the number and type of memory errors on your system, use the show memory scan EXEC command.
show memory scan
Defaults
No default behavior or values
Command Modes
EXEC
Command History
Example
The following example monitors the number and type of parity errors on your system:
Router# show memory scanMemory scan is on.No parity error has been detected.