International Business Machines Corporation

Douglas A Martin

Brent Cameron Beardsley

Michael T Benhase

Robert Louis Morton

Kenneth Wayne Todd

Mark Albert Reid

Gail Andrea Spear

Susan Kay Candelaria

Thomas Charles Jarvis

Vern J Legvold

Joseph Smith Hyde

Peter L Leung

Disclosed is a method, system, and article of manufacture for processing modified meta data for data recovery operations. The meta data provides information on user data maintained in a storage device. The system determines whether meta data tracks maintained in a cache were modified and indicates in a non-volatile memory that the determined meta data tracks were modified. Data recovery operations may be initiated as a result of a system failure, such as a warmstart or coldstart recovery. During such data recovery operations, the system processes the non-volatile memory and the indications of modified meta data tracks therein to rebuild lost meta data tracks in the cache.

Method and system for recovery of meta data in a storage controller

Disclosed is a method, system, and article of manufacture for managing meta data. The meta data provides information on data maintained in a storage device. The system receives a request for meta data from a process and determines whether the requested meta data is in cache. After determining that the requested meta data is not in cache, the system determines whether there are a sufficient number of allocatable segments in cache to stage in the meta data and allocates segments in cache to store the meta data after determining that there are enough allocatable segments in cache. The system stages the requested meta data into the allocated segments. Alternatively, after determining that the requested meta data is in cache, the system determines whether a second process has exclusive access to the meta data in cache. After determining that the second process does not have exclusive access, the system indicates to the first process that access to the meta data is permitted. Otherwise, after determining that the second process has exclusive access, the system notifies the first process that access to the meta data track will be provided at a later time when the second process relinquishes exclusive access.

Method and system for managing meta data

Method, system, and program for managing meta data in a storage system and rebuilding lost meta data in cache

Disclosed is a system for caching data. After determining a sequential access of a first memory area, such as a direct access storage device (DASD), a processing unit stages a group of data sets from the first memory area to a second memory, such as cache. The processing unit processes a data access request (DAR) for data sets in the first memory area that are included in the sequential access and reads the requested data sets from the second memory area. The processing unit determines trigger data set from a plurality of trigger data sets based on a trigger data set criteria. The processing unit then stages a next group of data sets from the first memory area to the second memory area in response to reading the determined trigger data set.

Method and system for staging data into cache

Disclosed is a system for managing data in cache. A list of data entries in a first memory area has a first end and a second end, such as a most recently used (MRU) end and least recently used (LRU) end. A first pointer addresses a data entry in the list and a second pointer addresses another data entry in the list that is not at the first and second ends. Data from a second memory area is provided to add to the list. A determination is made as to whether the provided data to add to the list is one of a first type and second type of data, such as sequentially accessed data or non-sequentially accessed data. The provided data is stored in the first memory area as a new data entry in the list. The first pointer is modified to address the new data entry after determining that the provided data is of the first type. After determining that the provided data is of the second type, the second pointer is processed to determine where to add the new data entry to the list between the first and second ends.

Method and system for managing data in cache

Disclosed is a cache management scheme using multiple data structure. A first and second data structures, such as linked lists, indicate data entries in a cache. Each data structure has a most recently used (MRU) entry, a least recently used (LRU) entry, and a time value associated with each data entry indicating a time the data entry was indicated as added to the MRU entry of the data structure. A processing unit receives a new data entry. In response, the processing unit processes the first and second data structures to determine a LRU data entry in each data structure and selects from the determined LRU data entries the LRU data entry that is the least recently used. The processing unit then demotes the selected LRU data entry from the cache and data structure including the selected data entry. The processing unit adds the new data entry to the cache and indicates the new data entry as located at the MRU entry of one of the first and second data structures.

Method and system for managing data in cache using multiple data

A system and technique for storing data in a cache memory in record format and in track format. Space is allocated in cache memory for the storage of data in track format. Additional space is allocated for the storage of data in record format. Data is stored in both formats. The most current data is identified and addresses are generated for each record of data. Access to individual records of data is facilitated through a track information block in which pointers are stored for the most current records whether stored in track format or record format. The track information block facilitates a rapid storage and retrieval of data in either format. In a specific implementation, data is stored in either format in cache using a scatter index table. The scatter index table and associated track directory entries are stored in a shared control array. Each track directory entry points to a track slot header in a cache. The track slot header points to an area (segment) in the cache memory in which selected data resides. The track slot header also points to a track information block associated with the selected segment. The track information block identifies the location selected records in the segment in track format or record format.

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Tucson, AZ, United States of America

Douglas A Martin