To improve performance and resolve
bottlenecks, you can specify how input and output data is buffered. Although
the size and operation of the buffer are usually the same for all links on all
stages, you can modify the settings for specific links.
By default, data is
buffered so that no deadlocks occur. Be careful when changing data buffering
settings because specifying inappropriate values might create a deadlock.
Any changes that you make to the
properties on the Advanced tab are automatically reflected on
the Advanced tab of the stage at the other end of the link.
To change the settings for data
buffering:
1.
double-click the Stage.
2.
In the Input/Output/stage editor, select the link that you want to
edit.
3.
On the Advanced tab, select one of the following
options for the Buffering mode:
(Default) Select this option to use the setting
that is specified by the environment
variable APT_BUFFERING _POLICY. The default setting for this environment
variable is AUTOMATIC_BUFFERING.
variable APT_BUFFERING _POLICY. The default setting for this environment
variable is AUTOMATIC_BUFFERING.
Auto buffer Select this option to buffer data only
when buffering is required to prevent
at a flow deadlock.
at a flow deadlock.
Buffer Select this option to buffer all
data for this link.
No buffer Select this option to perform no
buffering. Selecting this option might result
in deadlocks.
in deadlocks.
4.
If you selected Auto buffer or Buffer,
specify the following values:
a.
Maximum memory buffer size (bytes): Specify the maximum
amount of virtual memory, in bytes, to use for each buffer. The default size is
3145728 (3 MB).
b.
Buffer free run (percent): Specify how much of
the available in-memory buffer to consume before the buffer writes to disk. The
value ofBuffer free run is expressed as a percentage of Maximum
memory buffer size. When the amount of data in the buffer consumes less
than the percentage that is specified for Buffer free run, new data
is accepted automatically. When the data exceeds this percentage, the buffer
tries to write some of the data that it contains before accepting more data.
The default value is 50%. You can set this value to greater than 100%, in which
case the buffer continues to store data up to the specified percentage before
writing to disk.
c.
Queue upper bound size (bytes): Specify the maximum
amount of data, in bytes, that can be buffered, including data that is buffered
in memory and on disk. The default, 0, means that the buffer size is limited
only by the value that is specified for resource scratchdiskin the
WebSphere® DataStage configuration file. If you specify a value for Queue
upper bound size, the amount of data in the buffer cannot exceed this value
(in bytes) plus the size of one block (32 KB).
d.
Disk write increment (bytes): Specify the size,
in bytes, of blocks of data that are moved to and from disk by the buffering
operator. The default value is 1048576 (1 MB). When you specify a value for
this parameter, consider your needs for decreasing disk access and for
increasing throughput. For example, specifying a larger block size reduces disk
activity, but might decrease performance when data is written in smaller units.
Likewise, specifying a smaller block size increases data throughput, but might
increase disk activity.
5.
Click OK to save your changes and close the stage
editor.
njoy the simplicity.......
Atul Singh
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