Abstract: A request to access data programmed to a memory sub-system is received. A determination is made of whether a memory device that stores the data referenced by the request satisfies a weak memory device criterion in view of a quality rating for the device. In response to a determination that the memory device satisfies the weak memory device criterion, an error correction operation to access the data is performed in accordance with the request.

Abstract: A system for determining relationships between hierarchically structured schema components and their effects on and content of tuples, includes: analyzing the hierarchically structured schema with user-supplied mappings and finding elements or attributes mapped to a same relational table; determining relationships between the elements or attributes to be either a one-to-one relationship or a one-to-many relationship based on an information set in the hierarchically structured schema; recording the relationships; and processing a hierarchically structured document against the recorded relationships and generating tuples accordingly. The constructs of a hierarchically structured schema that may affect the cardinality between the attributes of a relation, and thus the contents of the tuples, are considered. A relationship between the hierarchically structured schema model and a relational model is established.

Abstract: In a storage system comprising an array of storage devices including a processor and memory, a plurality of data blocks are organized on the storage devices in segments striped across the storage devices. A main directory, stored in memory, contains the location on the storage device of each of the data blocks. For each segment a segment directory having information on the data blocks in the segment is stored on the storage devices. When a damaged segment directory is detected, a checkpoint of the main directory is written to the storage devices. A list is maintained of damaged segment directories such that segments on the damaged segment directories list are not garbage collected. Following a main directory recovery procedure, the damaged segment directories are reconstructed using the main directory.

Abstract: In a storage system comprising an array of storage devices including a processor and memory, a plurality of data blocks are organized on the storage devices in segments striped across the storage devices. A main directory stored in memory contains the location on the storage device of each of the current data blocks. A method is provided for recovering a main directory in the event that the main directory becomes damaged. A segment directory having information on the data blocks in the segment is stored as part of the segment on the storage devices. Periodically a checkpoint of the main directory is written to the storage devices. A list is maintained of closed segments written to the storage devices since the checkpoint directory was written to the storage devices.