How Oracle Works on Exadata - Oracle Exadata Recipes: A Problem-Solution Approach - page 63

At system startup, Oracle runs /etc/init.d/cell.d . /etc/init.d/cell.d executes as the celladmin operating
system account and runs “alter cell startup services rs ” to start the Restart Server. After sleeping for a bit, the script
runs “ alter cell startup services all, ” which starts up remaining processes including cellsrv and MS . Logic
exists within /etc/init.d/cell.d as well as /etc/init.d/precell to determine whether any failures or improper
configurations exist. If so, Oracle will attempt to start from the last good status.
cellsrv is the primary process/software that runs on the storage servers. If you look at the process hierarchy
(excluding OSWatcher processes) from the output listed in the Solution of this recipe, here's what it means:

• The

cellrssrm process is the main Restart Server process. It launches three helper processes:
cellrsomt , cellrsbmt , and cellrsmmt .
The •

cellrsomt helper process is ultimately responsible for launching cellsrv .

• The

cellrsbmt and cellrsmmt processes are additional helper processes responsible for
launching cellrsbkm and the main Management Server Java process.

•

cellrssmt is called by cellrsbkm , and its ultimate goal is to ensure cell configuration files are
valid, consistent, and backed up.

cellsrv is the main process that performs I/O on the Exadata cell.
cellsrv is a multithreaded process that essentially facilitates I/O requests from the compute nodes. It receives
and unpacks iDB messages transmitted over the InfiniBand interconnect and examines metadata contained in the
messages to determine the appropriate course of action. For example:

• And of course,

• If the request contains information that indicates a full scan via direct read,

cellsrv can

perform a Smart Scan.

• If the request is for a single-block read,

cellsrv performs as a traditional block I/O server.
If the request is tagged with data that falls within a bucket of conditions specified by an

•

enabled I/O Resource Management plan, cellsrv will queue and prioritize I/O requests
accordingly.

There are many other special activities that cellsrv performs and, in general, you can think of cellsrv as an
intelligent set of I/O processes that execute different sections of Oracle code depending on data contained in the iDB
messages. The iDB messages are essentially instructions that will result physical disk I/O, based on the data being
requested and the metadata encapsulated in the iDB messages. In short, cellsrv is responsible for receiving I/O
instructions and utilizing any and all unique Exadata software features along the way.

■ idB = Intelligent database protocol, which is a network protocol designed by oracle to facilitate InfiniBand
aware I/o communication.

Note

The Management Server, or MS , provides a Java interface to the CellCLI command line interface, as well as
providing an interface for Enterprise Manager plugins. If MS is down, you won't be able to use cellcli .
The Restart Server, or RS , is a set of processes responsible for managing and restarting other processes.
In addition to the three main programs, Oracle runs OSWatcher on storage cells to collect performance metrics
and publishes these to the OSWatcher archive directories.
Together, the three main storage cell programs are key components of the Exadata Storage Server software and
overall functionality.