LMDB: question about MDB_RESERVE

Hello all,

I have a question about the MDB_RESERVE flag. The documentation in some places says "reserve space for data of the given size, but don't copy the given data. Instead, return a pointer to the reserved space, which the caller can fill in later - before the next update operation or the transaction ends."

My question is specifically about the "before the next update operation or the transaction ends" part. Does this mean the reserved buffer becomes unusable as soon as another put is executed? What exactly happens? This statement does not appear consistently, which is why I am doubting..

thanks + happy holidays, Chris