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Ha,formerly the suggested symbol for the name hahnium, which was applied variously to two elements, now called dubniumdubnium
, artificially produced radioactive chemical element; symbol Db; at. no. 105; mass number of most stable isotope 268; m.p., b.p., and sp. gr. unknown; valence +5.
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, artificially produced radioactive chemical element; symbol Hs; at. no. 108; mass number of most stable isotope 277; m.p., b.p., sp. gr., and valence unknown. Situated in Group 8 of the periodic table, it is expected to have properties similar to those of osmium.
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HAAbbrev. for hour angle.
high availabilityAlso called "RAS" (reliability, availability, serviceability) or "fault resilient," it refers to a multiprocessing system that can quickly recover from a failure. There may be a minute or two of downtime while one system switches over to another, but processing will continue. This is not the same as fault tolerant, in which redundant components are designed for continuous processing without skipping a heartbeat.
High availability also refers to being able to service a component in the system without shutting down the entire operation. See clustering and hot fix.