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What are environmental variables and how are they
used?
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Environment variables enable you to set the project
defaults and these are used in jobs.
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What is the DSParams file?
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For any datastge project, all project levels, user
defined environmental items are stored in a file called DSParams.
It is located in <dshome>\DataStage\Projects\<projname>.
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How do I copy the DSParams file the first time as
opposed to copying from one project to another project?
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The methodology described below provides a workaround
for moving or sharing the global parameters without having to re-type
them in the administrator. The work around consists of replacing and/or
editing this file to add the parameters. Be sure to back up the original
file before any other activity occurs.
For a new project that has not yet defined any global parameters, just copy the existing
DSParams file to the new project. Be sure to rename the existing DSParams
file. Ensure all DS clients (Designers, etc.) are logged off, and
stop and start the DataStage services to activate it. Then go into
the DataStage Administrator and all the parameters should be visible
in the user-defined section of the environment screen. At this point,
edit the default values for each parameter.
For an existing project that has already defined some global parameters; the DSParams file
must be edited to add the desired parameters. The process below describes
how to do this. The user-defined parameters are in two sections of
the DSParams file: one section defines the parameters [EnvVarDefns]
and the second section contains the default values [EnvVarValues].
The approach is to copy the correct lines from the original source
project file into the target project DSParams file:
Rename/Backup the DSParams file
in the target project directory and backup the source project DSParams
file as well.
Edit the source project DSParams.
Go to the end of the [EnvVarDefns] section and find the user defined
parameters, which are at the end of the section. Select the lines
up to but not including the line which contains [PROJECT]".
Copy these lines and paste them
into the target project DSParams file before the "[PROJECT]" section.
Go back and edit the source project
DSParams file. Find the section starting with the line "[EnvVarValues]".
This is usually at the end of the file. Copy all of the lines of that
section, or select all the lines for the specific parameters to be
moved.
Locate the end of the DSParams
file in the target project directory. See if it has a section called
"[EnvVarValues]". If it does not, add it. If it does, then go to the
next step.
Paste the lines into the target
project DSParams file at the end of the "[EnvVarValues]" section and
before the end of file.
Save the DSParams file in the
target project directory.
Ensure all DS clients (designers
and so forth) are logged off, and stop and start the DataStage services
to activate it. Then go into the DataStage Administrator and all the
parameters should be visible in the user-defined section of the environment
screen. At this point, change the default values for each parameter.
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What are 'Array' and 'Transaction' sizes?
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Array
Size: Array size is a parameter to specify the number of
rows written (to a database) at a time. In other words it refers to
the number of rows that are transferred in one call between DataStage
and the database before they are written.
Generally,
increasing the array size will increase performance since client memory
is used to cache records resulting in lesser server hits. The maximum
size for array size is 32767. But increasing the array size too much
will result in strain on the client memory. Hence an optimal value
must be arrived at considering the client memory.
For flexibility this has been parameterized as a
environmental variable. Separate environmental variables are available
for each source as well as for OWS, OWE and MDW. For direct DRS lookups,
the recommended array size is 1 since DS lookups generally expects
1 row of data to be returned.
Transaction
Size: Transaction size refers to the number of rows that
are written to the database before the data is committed. Giving a
transaction size of zero will ensure that commit doesn't happen until
all the records are written. The default value is 0. If the transaction
size is set to 100 then the database table commits are performed every
100 rows. Here again an optimal value must be arrived at considering
the strain on the Database server and the number of records.
For flexibility this has also been parameterized as
a environmental variable. Separate environmental variables are available
for each source as well as for the OWS, OWE and MDW.
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How is the DATA_ORIGIN environment variable configured?
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The value for DATA_ORIGIN is 'S' for following loads:
The DATA_ORIGIN must be toggled to Enterprise only when running those sets
of jobs whose flow is from OWE to MDW.
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