Import/export element (I/O slot) addresses
I/O slots are virtualized by dynamically associating element addresses to them as required. The association of IEE addresses is accomplished in a way that is transparent to the application software.
You can select the number of IEE addresses for a logical library (as reported to the host application software by the SCSI Mode Page X'1D') by changing the Max VIO Slots setting for that logical library up to a value of 255. For each logical library, the default value for the quantity of that logical library's IEE addresses is 255.
With virtual import/export element addressing, the IEE address range includes addresses from 769 (X'301') to 1023 (X'3FF'). This range allows for a maximum of 255 IEE addresses for each logical library.
Each logical library has a unique virtual IEE address space that is not accessible by other logical libraries. Virtual IEEs allow each logical library to use all 255 elements without impacting other logical libraries. For example, two logical libraries might both have 255 cartridges in virtual IEEs 769 - 1023, but the cartridges are located in different physical storage slots. Thus, competition for IEE space between logical libraries is eliminated and the effective quantity of IEEs is enhanced without physical modifications to the library. The automatic queuing of a cartridge's moves between the I/O station and the virtual storage slots makes it appear to the host application that the library contains more physical I/O slots than exist. Thus, instead of sharing a maximum of 10 I/O slot addresses in Frame 1, each logical library can have up to 255 I/O slot addresses that are not shared.