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

       /MAXCSTACK=x
       -ss x

    Each Java thread has two stacks: one for Java code and one for C
    code. The /MAXCSTACK option sets the maximum stack size that can
    be used by C code in a thread to x. Every thread spawned during
    the execution of the program passed to JAVA has x as its C 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 128 kilobytes (/MAXCSTACK=128k).