May be I did not explain the task: I have to save in IRIS exact 8 bytes.

For example:

byte[] bytes = {35, -14, 119, -4, -114, -59, 35, 14};
String salt = Base64.getEncoder().encodeToString(bytes);
The salt is "I/J3/I7FIw4=", its length is 12.

Do you mean that if I save "I/J3/I7FIw4=" through JPA, I'll get in IRIS exact 8 bytes {35, -14, 119, -4, -114, -59, 35, 14}?

I've just tried it on, It seams it does not work: SQLCODE: <-105>

P.S. The only way I've found for now is plain JDBC and setBinaryStream() method.

Thanks

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