"The length of the request is 15 characters, not 16. You have told BPXWDYN that the X'00' is part of the request."
From what I gather reading the reference Paul Gilmartin posted, the null-terminator byte should be included in the length: http://www.ibm.com/support/knowledgecenter/SSLTBW_2.3.0/com.ibm.zos.v2r3.bpxb600/retparml.htm Note: {45,"rtdsn"} for the DSNAME request return area, while max DSNAME length is 44.
