Maintaining System Memory Configuration Guide, Cisco IOS Release 15M&T
Maintaining System Memory
Maintaining System Memory
Last Updated: December 1, 2012
Maintaining system memory enables you to configure, use and monitor the different types of memory on your router.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 module.
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.
Prerequisites for Maintaining System Memory
Restrictions for Maintaining System Memory
Information About Maintaining System Memory
Your router has many different locations where it can store images, configuration files, and microcode. Refer to your hardware documentation for details on which types of memory your routing device contains, where files can be stored (saved), and where images and boot images are located by default. This section provides information on the following memory types:
Dynamic random-access memory (DRAM) contains two types of memory:
On the Cisco 3600 series routers, you can use the memory-sizeiomem command to configure the proportion of DRAM devoted to main memory and to shared memory.
DRAM often comes on dual in-line memory modules (DIMMs).
Erasable programmable read-only memory (EPROM) is often referred to simply as ROM. On Cisco devices, the EPROM often contains the following:
Non-volatile random-access-memory (NVRAM) stores the following information:
Flash memory stores the Cisco IOS software image. On most platforms, it can store boot-images and/or configuration files.
Depending on the hardware platform, Flash memory might be available as EPROM, single in-line memory modules (SIMMs), dual in-line memory modules (DIMMs), or Flash memory cards. Check the appropriate hardware installation and maintenance guide for information about types of Flash memory available on a specific platform.
Depending on the platform, Flash memory is available in the following forms:
A Flash memory card that is inserted in to a Personal Computer Memory Card International Association (PCMCIA) slot. This card is used to store system images, boot images, and configuration files.
Ma ny Cisco routers load the system image from flash storage into RAM in order to run the Cisco IOS. However, some platforms, such as the Cisco 1600 Series and Cisco 2500 Series, execute the Cisco IOS operation system directly from Flash memory. These platforms are run-from-Flash memory systems.
If you want to partition Flash memory, you must use a relocatable image. Relocatable images can be run from any location in Flash and can download images to any location. If you are upgrading from a nonrelocatable image to a relocatable image, you must erase Flash memory during the download so that the image is downloaded as the first file in Flash memory. All images for run-from-Flash platforms from Cisco IOS Release 11.0 and later are relocatable. See the " Image Naming Conventions " section in the "Loading and Maintaining System Images" chapter to determine if your images are run-from-Flash images or are relocatable.
Flash memory provides write protection against accidental erasing or reprogramming. Some platforms have a write-protect jumper which can be removed to prevent reprogramming of Flash memory. You must install the jumper when programming is required. Some platforms have write protect switched on Flash memory cards that you can use to protect data. You must set the switch to unprotected to write data to the Flash memory card. Refer to your hardware documentation for information on security jumpers and write protect switches.
Partition of Flash Memory
On most Class B Flash file systems, you can partition banks of Flash memory into separate, logical devices so that the router can hold and maintain two or more different software images. This partitioning allows you to write software into Flash memory while running software in another bank of Flash memory.
Systems that Support Partitioning
To partition Flash memory, you must have at least two banks of Flash memory; a bank is a set of 4 chips. This requirement includes systems that support a single SIMM that has two banks of Flash memory. The minimum partition size is the size of a bank.
Benefits of Partitioning Flash Memory
Partitioning Flash memory provides the following benefits:
Flash Load Helper Versus Dual Flash Bank
Flash load helper is a software option that enables you to upgrade system s oftware on run-from-Flash systems that have a single bank of Flash memory. It is a lower-cost software upgrade solution than dual-bank Flash, which requires two banks of Flash memory on one SIMM. Flash load helper is only available on run-from-Flash platforms, such as the Cisco 2500 series, Cisco 3000, and Cisco 5200.
You might use Flash load helper rather than partitioning Flash into two banks for one of the following reasons:
See the "Downloading Files Using the Flash Load Helper " section for information about using Flash load helper.
Use of the Flash Load Helper to Upgrade Software on Run-from-Flash Systems
Flash load helper is a software option that enables you to upgrade system s oftware on run-from-Flash systems that have a single bank of Flash memory. It is a lower-cost software upgrade solution than dual-bank Flash, which requires two banks of Flash memory on one SIMM.
The Flash load helper software upgrade process is simple and does not require additional hardware; however, it does require some brief network downtime. A system image running from Flash can use Flash load helper only if the boot ROMs support Flash load helper. Otherwise, you must perform the Flash upgrade manually.
Flash load helper is an automated procedure that reloads the ROM-based image, downloads the software to Flash memory, and reboots to the system image in Flash memory. Flash load helper performs checks and validations to maximize the success of a Flash upgrade and minimize the chance of leaving Flash memory either in an erased state or with a file that cannot boot.
In run-from-Flash systems, the software image is stored in and executed from the Flash EPROM rather than from RAM. This method reduces memory cost. A run-from-Flash system requires enough Flash EPROM to hold the image and enough main system RAM to hold the routing tables and data structures. The system does not need the same amount of main system RAM as a run-from-RAM system because the full image does not reside in RAM. Run-from-Flash systems include the Cisco 2500 series and some Cisco 3000 series.
Flash Load Helper Features
Flash load helper performs the following functions:
Flash load helper can also be used on systems with multiple banks of Flash memory that support Flash memory partitioning. Flash load helper enables you to download a new file into the same partition from which the system is executing an image.
For information about how to partition multiple banks of Flash memory so your system can hold two different images, see the "Partitioning Flash Memory " section.
Allocation of DRAM Memory for the Cisco 3600 Series
DRAM memory in Cisco 3600 series routers is organized as one contiguous address space divided between processor memory and I/O memory. Depending on the type and number of network interfaces you have configured in the router, you may need to reallocate the DRAM memory partitioned to processor memory and I/O memory.
Cisco manufacturing configures most Cisco 3600 series routers to have 25 percent of the address space allocated to I/O memory and 75 percent allocated to processor memory. But for customer orders that require two or more ISDN PRI interfaces, DRAM memory is configured to provide 40 percent of the address space for I/O memory and 60 percent for processor memory. (See the figure below.) Cisco Systems performs these DRAM memory adjustments before it ships each router.
However, there are cases where you may have to manually reallocate the DRAM memory split between processor memory and I/O memory after you have received a router from Cisco Systems.
For example, suppose you receive a Cisco 3640 router with the following running configuration:
Later, however, you add a 4-port ISDN BRI network module to the router. You now have 12 ISDN BRI interfaces running on the router. At this point, you must use the memory-sizeiomem command to configure 40 percent of the address space for I/O memory and 60 percent for processor memory.
Memory Scan on the Cisco 7500 Series
On Cisco 7500 series routers (including 7000 series with the RSP7000 card upgrade), a memory scanning feature is available. This 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 memoryscan and showmemoryscan command-line interface (CLI) commands.
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:
How to Configure System Memory Parameters
Displaying System Memory Information
[all | chips |filesys]
][all | chips | detailed | err | summary]
Partitioning Flash Memory
To partition Flash memory, complete the tasks in this section.
Downloading Files Using the Flash Load Helper
To download a new file to Flash memory using Flash load helper, check to make sure that your boot ROMs support Flash load helper and then complete the tasks in this section:
2. Do one of the following:
The following error message displays if you are in a Telnet session and the system is set for manual booting (the boot bits in the configuration register are zero):
ERR: Config register boot bits set for manual booting
In case of any catastrophic failure in the Flash memory upgrade, this error message helps to minimize the chance of the system going down to ROM monitor mode and being taken out of the remote Telnet user's control.
The system tries to bring up at least the boot ROM image if it cannot boot an image from Flash memory. Before reinitiating the copy:command, you must set the configuration register boot field to a nonzero value, using the config-register global configuration command.
The copy command initiates a series of prompts to which you must provide responses. The dialog is similar to the following:
Router# copy tftp: flash: *************************** NOTICE ******************************* Flash load helper v1.0 This process will accept the TFTP copy options and then terminate the current system image to use the ROM based image for the copy. Router functionality will not be available during that time. If you are logged in via telnet, this connection will terminate. Users with console access can see the results of the copy operation. ****************************************************************** There are active users logged into the system. Proceed? [confirm] y System flash directory: File Length Name/status 1 2251320 abc/igs-kf.914 [2251384 bytes used, 1942920 available, 4194304 total] Address or name of remote host [255.255.255.255]? 172.16.1.111 Source file name? abc/igs-kf.914 Destination file name [default = source name]? <Return> Accessing file 'abc/igs-kf.914' on 172.16.1.111.... Loading from 172.16.13.111: Erase flash device before writing? [confirm] n File 'abc/igs-kf.914' already exists; it will be invalidated! Invalidate existing copy of 'abc/igs-kf.914' in flash memory? [confirm] y Copy 'abc/igs-kf.914' from TFTP server as 'abc/igs-kf.914' into Flash WITHOUT erase? y %SYS-5-RELOAD: Reload requested % FLH: rxboot/igs-kf.914r from 172.16.1.111 to flash...
The Flash Load Helper operation verifies the request from the running image by trying to copy a single block from the remote server. Then the Flash load helper is executed, causing the system to reload to the ROM-based system image. If the file does not seem to be a valid image for the system, a warning is displayed and a separate confirmation is sought from you.
If the configuration has been modified but not yet saved, you are prompted to save the configuration:
System configuration has been modified. Save? [confirm]
Users with open Telnet connections are notified of the system reload, as follows:
**System going down for Flash upgrade**
If the copy process fails, the copy operation is retried up to three times. If the failure happens in the middle of a copy operation so that only part of the file has been written to Flash memory, the retry does not erase Flash memory unless you specified an erase operation. The partly written file is marked as deleted, and a new file is opened with the same name. If Flash memory runs out of free space in this process, the copy operation is terminated.
After Flash load helper finishes copying (whether the copy operation is successful or not), it automatically attempts an automatic or a manual boot, depending on the value of bit zero of the configuration register boot field according to the following:
To view the system console output generated during the Flash load helper operation, use the image that has been booted up after the Flash memory upgrade. Enter the moreflh:logfilecommand in privileged EXEC mode.
If you are a remote Telnet user performing the Flash upgrade without a console connection, this task allows you to retrieve console output when your Telnet connection has terminated due to the switch to the ROM image. The output indicates what happened during the download, and is particularly useful if the download fails.
Formatting Flash Memory
On Class A and Class C Flash file systems, you can format Flash memory. Formatting erases all information in Flash memory.
On the Cisco 7000 family, you must format a new Flash memory card before using it in a PCMCIA slot.
Flash memory cards have sectors that can fail. You can reserve certain Flash memory sectors as "spares" for use when other sectors fail. Use the format command to specify between 0 and 16 sectors as spares. If you reserve a small number of spare sectors for emergencies, you do not waste space because you can use most of the Flash memory card. If you specify zero spare sectors and some sectors fail, you must reformat the Flash memory card and thereby erase all existing data.
The format operation requires at least Cisco IOS Release 11.0 system software.
Flash Memory Formatting Process
Use the following procedure to format Flash memory. If you are formatting internal Flash memory, such as bootflash, you can skip the first step. If you are formatting a Flash memory card, complete both steps:
1. Insert the new Flash memory card into a PCMCIA slot. Refer to instructions on maintaining the router and replacing PCMCIA cards in your router's hardware documentation for instructions on performing this step.
2. Enter the format [spare spare-number ] device1: [[device2:][monlib-filename ]]command to format Flash memory.
The following example shows the format command that formats a Flash memory card inserted in slot 0.
Router# format slot0: Running config file on this device, proceed? [confirm]y All sectors will be erased, proceed? [confirm]y Enter volume id (up to 31 characters): <Return> Formatting sector 1 (erasing) Format device slot0 completed
Recovering from Locked Blocks
Valid I/O memory percentage values are 10, 15, 20, 25, 30, 40 (the default), and 50. I/O memory size is the specified percentage of total memory size, rounded down to the nearest multiple of 1 MB. A minimum of 4 MB of memory is required for I/O memory. The remaining memory is processor memory.
The memory-sizeiomem command does not take effect until you save it to NVRAM using the copysystem:running-confignvram:startup-config EXEC command and reload the router. However, when you enter the command, the software checks whether the new memory distribution leaves enough processor memory for the currently running Cisco IOS image. If not, the following message appears:
Warning: Attempting a memory partition that does not provid e enough Processor memory for the current image.If you write memory now, this version of so ftware may not be able to run.
When you enter the reload command to run a new image, the software calculates the new processor and I/O memory split. If there is not enough processor memory, it automatically reduces I/O memory to an alternative setting to load the image. If there is still not enough processor memory for the image to run, then you do not have enough DRAM.
The following example allocates 40 percent of DRAM to I/O memory and the remaining 60 percent to processor memory. The example views the current allocation of memory, changes the allocation, saves the allocation, and reloads the router so the changes can take effect. In the showmemorycommand output, the Free(b) column shows how much I/O memory is available:
Router# show memory Head Total(b) Used(b) Free(b) Lowest(b) Largest(b) Processor 60913730 3066064 970420 2095644 2090736 2090892 I/O C00000 4194304 1382712 2811592 2811592 2805492 --More-- Router# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)# memory-size iomem 40 Router(config)# exit Router# Router# copy system:running-config nvram:startup-config Building configuration... [OK] Router# reload rommon > boot program load complete, entry point: 0x80008000, size: 0x32ea24 Self decompressing the image : ###################################################################################################################################################################################################################################################### [OK]
Configuring and Verifying Memory Scan on the Cisco 7500 Series
To configure and verify memory scan on the Cisco 7500 series router, complete the tasks in this section:
1. Use the memoryscan command in global configuration mode to enable the feature.
2. Use the moresystem:running-configuration command in privileged EXEC mode to verify that memory scan appears in the running configuration.
3. Use the showmemoryscancommand to monitor the number and type of parity errors on your system.
Use the showmemoryscan command in privileged EXEC mode. In the following example, the feature is enabled and no parity errors are found:
Router# show memory scan Memory scan is on. No parity error has been detected.
If the Memory Scan feature has not been configured, or has been turned off, the showmemoryscan command generates a report. In the following example, Memory Scan is turned off:
Router# show memory scan Memory scan is off No parity error has been detected.
If errors are detected in the system, the showmemoryscan command generates an error report. In the following example, Memory Scan detected a parity error:
Router# show memory scan Memory scan is on. Total Parity Errors 1. Address BlockPtr BlckSize Disposit Region Timestamp 6115ABCD 60D5D090 9517A4 Scrubed Local 16:57:09 UTC Thu Mar 18Cisco 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)
Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: 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. (1110R)
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.
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