struct PK_SESSION_start_o_s
    {
    int     o_t_version;  --- version number of this option structure
    char   *journal_file; --- name of journal file (NULL)
    int     user_field;   --- size of user fields in integers (0)
    int     reserved;     --- for future use (1)
    };
typedef struct PK_SESSION_start_o_s PK_SESSION_start_o_t;


Specific Errors:
    PK_ERROR_bad_filename          journal_file is not a valid file name
    PK_ERROR_bad_user_field_size   user field length is negative or longer
                                   than the maximum


This is the option structure for PK_SESSION_start.  Its fields are as follows:

  journal_file - the name of the required journal file.  If this is set to a
                 non-empty string, then journalling is enabled to a file of
                 the given name.  If it is set to NULL or the empty string
                 then journalling is not enabled.
  user_field   - the size of user fields in integers.  The maximum length is
                 16.  If it is set to zero then no user fields will be
                 allocated.  Note that in order to receive an archived part
                 with its user fields, it is necessary that the user field
                 length for the current session is the same as that for the
                 session when the part was archived.