Oracle Tips and Tricks — David Fitzjarrell

December 15, 2013

To DMA, Or Not To DMA

Filed under: Exadata — dfitzjarrell @ 12:35

Exadata is a different system for a DBA to administer. Some tasks in this environment, such as running the exachk script, require root O/S privileges. This script can be run by the system administrator, and this will be the case if you are managing Exadata as a DBA. However, a new role has emerged relative to Exadata, that of the Database Machine Administrator, or DMA. Let’s look at what being a DMA really means.

In addition to the usual DBA skillset, the DMA must also be familiar with, and be able to understand, the following management and monitoring commands on the specified systems.

On the compute nodes (database nodes):

Linux: top , mpstat , vmstat , iostat , fdisk , ustat , sar , sysinfo
Exadata: dcli
ASM: asmcmd , asmca
Clusterware: crsctl , srvctl

On the storage servers/cells:

Linux: top , mpstat , vmstat , iostat , fdisk , ustat , sar , sysinfo
Cell management: cellcli , cellsrvstat

Being a DMA also includes other areas of responsibility not associated with being a DBA. The following table summarizes the areas of responsibility for a DMA:

*******DMA Responsibilities *******
Skill Percent
System Administrator 15
Storage Administrator 0
Network Administrator 5
Database Administrator 60
Cell Administrator 20

The ‘Percent’ column indicates the percentage of the overall Exadata system requiring this knowledge, and as you can see if you’ve been an 11g RAC administrator, you have 60 percent of the skillset required to be a DMA. Notice that storage administration knowledge is not necessary; this is because Exadata uses a different storage model than normal, a model where the database servers (or nodes) have no direct access to the storage and must access it through the storage servers. Also the number of available disks is dependent upon the number of available storage servers, with each storage server managing 12 physical disks. For many Exadata installations a separate server is configured to communicate with Exadata and with Oracle to provide information on hardware and firmware problems and/or failures; this system notifies Oracle Customer Support of the issue, generates any parts orders and notifies the Oracle technician when to pick up the delivered parts and dispatches the techician to the site to effect the repairs/replacements. Unless there is an external SAN or NAS device connected to Exadata to store database backups and exports there isn’t much need for a Storage Administrator. The remaining skills necessary to be a DMA are not difficult to learn and master. The Cell Administrator commands you will need ( cellcli , dcli ) will increase your knowledge to 80 percent of the DMA skillset. CellCLI is the command-line interface to monitor and manage the storage cells. There are three supplied logins to each storage cell and these are ‘root’, ‘cellmonitor’ and ‘celladmin’. As you can probably guess ‘celladmin’ is the most powerful login that isn’t ‘root’ (the superuser in Linux and Unix). You can do most anything to the storage cells, including startup and shutdown, with ‘celladmin’. The ‘cellmonitor’ user can generate reports and list attributes from the storage cells but has no authority to perform management tasks. The full list of available cellcli commands is shown below:

CellCLI> help

 HELP [topic]
   Available Topics:
        ALTER
        ALTER ALERTHISTORY
        ALTER CELL
        ALTER CELLDISK
        ALTER GRIDDISK
        ALTER IBPORT
        ALTER IORMPLAN
        ALTER LUN
        ALTER PHYSICALDISK
        ALTER QUARANTINE
        ALTER THRESHOLD
        ASSIGN KEY
        CALIBRATE
        CREATE
        CREATE CELL
        CREATE CELLDISK
        CREATE FLASHCACHE
        CREATE FLASHLOG
        CREATE GRIDDISK
        CREATE KEY
        CREATE QUARANTINE
        CREATE THRESHOLD
        DESCRIBE
        DROP
        DROP ALERTHISTORY
        DROP CELL
        DROP CELLDISK
        DROP FLASHCACHE
        DROP FLASHLOG
        DROP GRIDDISK
        DROP QUARANTINE
        DROP THRESHOLD
        EXPORT CELLDISK
        IMPORT CELLDISK
        LIST
        LIST ACTIVEREQUEST
        LIST ALERTDEFINITION
        LIST ALERTHISTORY
        LIST CELL
        LIST CELLDISK
        LIST FLASHCACHE
        LIST FLASHCACHECONTENT
        LIST FLASHLOG
        LIST GRIDDISK
        LIST IBPORT
        LIST IORMPLAN
        LIST KEY
        LIST LUN
        LIST METRICCURRENT
        LIST METRICDEFINITION
        LIST METRICHISTORY
        LIST PHYSICALDISK
        LIST QUARANTINE
        LIST THRESHOLD
        SET
        SPOOL
        START

CellCLI>

All of the above commands are available to ‘celladmin'; only the LIST, DESCRIBE, SET and SPOOL commands are available to ‘cellmonitor’.

Networking commands that you may need are ifconfig , iwconfig , netstat , ping , traceroute , and tracepath . You may, at some time, also need ifup and ifdown , to bring up or bring down network interfaces, although using these commands will not be a regular occurrence. The following example shows how to bring up the eth0 interface.

# ifup eth0

It seems like a daunting task, to become a DMA, but it really isn’t that difficult. It does require a slightly different mindset, as you are now looking at, and managing, the entire system, rather than just the database. There will still be a need for a dedicated System Administrator and Network Administrator for your Exadata system, because, as a DMA, you won’t be responsible for configuration of these resources, nor will you be responsible for patching and firmware upgrades. The DMA is, essentially, assisting these dedicated administrators by assuming the day-to-day tasks these resources would provide. Being a DMA is also more useful to you and to the enterprise as the regular tasks for these areas can be performed by the person or persons who do most of the interaction with Exadata on a daily basis. Enterprises vary, however, and it may not be possible to assume the role of DMA as the division of duties is strictly outlined and enforced. It is good to know, though, that such a role exists and may be made available to you at some time in the future.

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2 Comments »

  1. Can I access celladmin without going through to the compute node?

    Comment by Nitha — July 2, 2014 @ 21:27 | Reply

    • You can login directly to each storage node and use cellsrv; dcli makes it a bit easier, I think, to access all of the available storage nodes from one central point. Remember celladmin is a user ACCOUNT, it’s not a utility.

      Comment by dfitzjarrell — July 3, 2014 @ 11:50 | Reply


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