/sys$common/syshlp/helplib.hlb JAVA, Qualifiers, /MAXJSTACK  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /MAXJSTACK=x
       -oss x

    Each Java thread has two stacks: one for Java code and one for
    C code. The /MAXJSTACK option sets the maximum stack size that
    can be used by Java code in a thread to x. Every thread spawned
    during the execution of the program passed to JAVA has x as its
    Java stack size. The default units for x are bytes. The value of
    x must be greater than or equal to 1000 bytes.

    You can modify the meaning of x by appending either the letter
    k for kilobytes or the letter m for megabytes. The default stack
    size is 400 kilobytes (/MAXJSTACK=400k).