A method for operating an automated data storage library, said automated data storage library comprising at least a plurality of multi-cartridge deep slot cells, each configured to store up to a plurality of data storage cartridges arranged in sequential order of tiers from front to rear, and comprising at least one accessor configured to selectively extract, place and transport data storage cartridges with respect to said multi-cartridge deep slot cells, said method comprising the steps of:
- operating said at least one accessor to selectively extract, place and transport data storage cartridges with respect to said multi-cartridge deep slot cells and with respect to other elements of said automated data storage library;
- and
- filling at least the frontmost tier of vacant said multi-cartridge deep slot cells in said selectively extracting, placing and transporting step in accordance with a predetermined algorithm, while leaving other tiers vacant.