--- a/src/Doc/System/Environment.thy Thu Jun 21 12:22:17 2018 +0200
+++ b/src/Doc/System/Environment.thy Thu Jun 21 12:39:52 2018 +0200
@@ -205,6 +205,11 @@
\<^descr>[@{setting_def ISABELLE_TMP_PREFIX}\<open>\<^sup>*\<close>] is the prefix from which any
running Isabelle ML process derives an individual directory for temporary
files.
+
+ \<^descr>[@{setting_def ISABELLE_TOOL_JAVA_OPTIONS}] is passed to the \<^verbatim>\<open>java\<close>
+ executable when running Isabelle tools (e.g. @{tool build}). This is
+ occasionally helpful to provide more heap space, via additional options like
+ \<^verbatim>\<open>-Xms1g -Xmx4g\<close>.
\<close>