ODS Graphics
uses Java technology to produce its graphs. Most of the time this
fact is transparent to you because the required Java Runtime Environment
(JRE) and Jar files are included with SAS software installation and
the Java environment is automatically started and stopped for you. When Java is started, it allocates a fixed amount of memory
that can grow up to the value set for the
-Xmx suboption in the JREOPTIONS option (discussed in a moment). This
memory is independent of the memory limit that SAS sets for the SAS
session with its MEMSIZE= option.
Normally,
the memory limit for Java is sufficient for most ODS Graphics applications.
However, some tasks are very memory intensive and might exhaust all
available Java memory, resulting in an OutOfMemoryError condition.
You might encounter Java memory limitations when
-
the product of the output size
and the DPI setting results in very large output
-
a classification panel has a very
large number of classifier crossings
-
a scatterplot matrix has a large
number of variables
-
creating 3D plots and 2D contours,
which are memory intensive to generate
-
a plot has a very large number
of marker labels
-
a plot uses many character variables
or has a large number of GROUP values
-
using the SG Editor to edit a graph
with a large amount of data.
If you
encounter a Java OutOfMemoryError, you can try executing your program
again by restarting SAS and specifying a larger amount of memory for
Java at SAS invocation.
To determine
what the current Java memory settings are, you can submit a PROC OPTIONS
statement that will show the value of the JREOPTIONS option:
proc options option=jreoptions;
run;
After
you submit this procedure code, a list of JREOPTIONS settings is displayed
in the SAS log. The JREOPTIONS option has many suboptions that configure
the SAS Java environment. Many of the suboptions are installation
and host specific and should not be modified, especially the ones
that provide installed file locations. For managing memory, look for
the
-Xms and
-Xmx suboptions:
Use this option to
set the minimum Java memory (heap) size, in bytes. Set this value
to a multiple of 1024 greater than 1MB. Append the letter k or K to
indicate kilobytes, or m or M to indicate megabytes. The default is
2MB. Examples:
-Xms6291456
-Xms6144k
-Xms6m
Use this option to
set the maximum size, in bytes, of the memory allocation pool. Set
this value to a multiple of 1024 greater than 2MB. Append the letter
k or K to indicate kilobytes, or m or M to indicate megabytes. The
default is 64MB. Examples:
-Xmx83886080
-Xmx81920k
-Xmx80m
As a general
rule, you should set the minimum heap size (
-Xms) equal to the maximum heap size (
-Xmx) to minimize garbage collections.
Typically,
SAS sets both
-Xms and
-Xmx to be about 1/4 of the total available
memory or a maximum of 128M. However, you can set a more aggressive
maximum memory (heap) size, but it should never be more than 1/2 of
physical memory.
You should
be aware of the maximum amount of physical memory your computer has
available. Let us assume that doubling the Java memory allocation
is feasible. So when you start SAS from a system prompt, you can add
the following option:
-jreoptions (-Xmx256m -Xms256m)
Aternatively,
you might need to specify the setting in quotation marks:
-jreoptions '(-Xmx256m -Xms256m)'
The exact
syntax varies for specifying Java options, depending on your operating
system, and the amount of memory that you can allocate varies from
system to system. The set of JRE options must be enclosed in parentheses.
If you specify multiple JREOPTIONS system options, SAS appends JRE
options to JRE options that are currently defined. Incorrect JRE options
are ignored.
If you
choose to create a custom configuration file, you would simply replace
the existing
-Xms and
-Xmx suboption values in the JREOPTIONS=(all
Java options) portion of the configuration file.
For more
information, see the SAS Companion for your operating system.