Unless otherwise noted, all String parameters that are either written to, or read from, a TR-31 key block will be in EBCDIC format. Input parameters are converted to ASCII before being written to the TR-31 key block and output parameters are converted to EBCDIC before being returned (see Appendix G. EBCDIC and ASCII Default Conversion Tables). TR-31 key blocks themselves are always in printable ASCII format as required by the ANSI TR-31 specification.

The TR-31 Optional Data Read callable service (CSNBT31R and CSNET31R) can be used in conjunction with the TR-31 Parse callable service (CSNBT31P and CSNET31P) to obtain both the standard header fields and any optional data blocks from the key block. This is generally a three-step process.

1. Use the TR-31 Parse callable service to determine how many optional blocks are in the TR-31 token. This is returned in the num_opt_blocks parameter.
2. Use keyword INFO with the TR-31 Optional Data Read callable service to obtain lists of the optional block identifiers and optional block lengths. Your buffers must be large enough to hold the returned data, but the required size can be determined from the number of blocks obtained in the step above.
3. Use keyword DATA with the TR-31 Optional Data Read callable service to obtain the data for a particular optional block, specified by the block identifier.

This table lists the required cryptographic hardware for each server type and describes restrictions for this callable service.

Table 122. TR-31 Optional Data Read required hardware

Server	Required cryptographic hardware	Restrictions
IBM zSeries 900	None
IBM zSeries 990 IBM zSeries 890	None
IBM System z9 EC IBM System z9 BC	None
IBM System z10 EC IBM System z10 BC	None
z196	None