A multifile system
is a specially created set of directories, possibly on different machines,
which have identical substructure.
Each directory is a
partition of the multifile system. When a multifile is placed in a multifile system,
its partitions are files within each of the partitions of the multifile system.
Multifile system
leads to better performance than flat file systems because multifile system can
divide your data among multiple disks or CPUs.
Typically (SMP
machine is exception) a multifile system is created with the control partition
on one node and data partitions on other nodes to distributes the work and
improve performance.
To do this use full
internet URLs that specifies file and directory names and location on remote
machines.
An Ab Initio multifile organizes all partitions of a multifile into one
single virtual file that you can reference as one entity
Following are
the steps to create a multifile directory for an application.
- Create the data and partitions directory to keep the data and control files.
- Execute the m_mkfs command from the data directory to create the multifile system.
Multifile
Commands
·
m_mkfs
·
m_mkdir
·
m_ls
·
m_expand
·
m_dump
·
m_cp
·
m_mv
·
m_rm
· m_touch
·
m_rollback
·
m_kill
·
m_env
·
m_env
-ev
m_mkfs
Command
m_mkfs will create
the mfs file system.
This command
is used to create a multifile system. Multifile system
consists of Control file directory along with the partitions directory. Control
file resides in the $APPL_DATA/mdata directory and data files in partitions
directories. Depending upon number of partitions multifile system will be
created.
Syntax:
m_mkfs <name of
the control partion> <URL of the first partion1> <URL of
the first partion1> <URL of the first partion1>.......
For eg:
m_mkfs controlpartion
c:abinitopartion1 c:abinitopartion2
c:abinitopartion3
Now controlpartion is
created under the root directory and the three partions are created under the
respective locations.
m_mkdir
Command
m_mkdir will
create the mfs file directory.
m_mkdir creates
a multidirectory. A multidirectory can span several different disks or nodes
and contains various items of metadata that are created and maintained by the
Ab Initio commands.
Syntax:
m_mkdir
url
url must
refer to a pathname within an existing multifile system.
m_ls
command
m_ls command to list
files & directories
Syntax:
m_ls
[opts...] url [url...]
m_expand
command
m_expand will
show the partitions used by a multifile.
Syntax:
m_expand
[opts...] path
m_expand commands takes
path rather than a file name to display the related information of partition.
m_dump
command
This command
displays contents of files, multifiles, or selected records from files or
multifiles
Syntax:
m_dump metadata [path] [opts ...]
m_cp
command
This command copies
files or multifiles that have the same degree of parallelism. Behind the
scenes, m_cp actually builds and runs a small graph, so it may copy from one
machine to another where Ab Initio is installed.
Syntax:
m_cp
source […] directory
m_mv
command
This command moves a
single file, multifile, directory, or multi-directory from one path to another
path on the same host via renaming… does not actually move data.
Syntax:
m_mv
oldpath newpath
m_rm
command
This command removes
a file or multifile and all its associated data partitions.
Syntax:
m_rm
[options] path [...]
m_touch
command
This command creates
an empty file or multifile in the specified location
Syntax:
m_touch
path
m_rollback
command
m_rollback winds
back an interupted Ab Initio graph. You need to find the graph's recovery file
in the execution directory and pass its name to m_rollback as in
Syntax:
m_rollback
<recovery file name>
m_kill command
m_kill stops a
graph and all the associated processes. Use this in preference to the Unix kill
command as the Unix command will only halt the single process it can see for
that graph whereas m_kill will halt everything associated with the graph. To
halt a running graph, then delete all the work files and changes it has made up
to that point, use the two commands
Syntax:
m_kill -9
<recovery file name>
m_rollback
-d <recovery file name>
m_env
command
m_env Dumps the
current Ab Initio environment settings to stdout.
m_env
-ev command
m_env -ev displays
the currently running version of the Co>Operating system.
m_eval
command
This
command to execute functions of ab-initio on Unix prompt.
It useful
for quickly testing out or debugging a complex expression
syntax:
m_eval
expression
Useful Links
| 1. | Ab Initio Sandbox |
| 2. | Ab Initio Components |
| 3. | Ab initio Parallelism |
| 4. | Ab Initio Basic Graph Development |
| 5. | Ab Initio Multifiles |
