What is a split?transaction, in the context of I/O and when may it be necessary?

What will be an ideal response?

Early computer backplane buses performed transactions, one at a time; for example, if the processor wrote to
memory, it accessed the bus, performed the write and then released the bus. Modern buses sometimes support
split transactions where a processor can request the bus and begin a transaction, release the bus, and then later
complete the transaction. The split transaction offers better bus utilization (without it there might be a delay
between a bus request and the eventual response).