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#### 10.2.2 Memory Size

If TOPCAT fails during operation with a message that says something about a `java.lang.OutOfMemoryError`, then your heap size is too small for what you are trying to do. You will have to run java with a bigger heap size using the `-Xmx` flag. Invoking TOPCAT from the `topcat` script you would write something like:

        topcat -Xmx256M ...

or using java directly:

        java -Xmx256M ...

which means use up to 256 megabytes of memory (don't forget the "M" for megabyte). JVMs often default to a heap size of 64M. You probably don't want to specify a heap size larger than the physical memory of the machine that you are running on.

There are other types of memory and tuning options controlled using options of the form `-X<something-or-other>`; if you're feeling adventurous you may be able to find out about these by typing "`java -X`".

Note however: using the `-disk` flag described in Section 10.1 may be a better solution; this makes the program store data from large tables on disk rather than in memory.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk