Abstract: Space on disk, designated for storage of recovery files is automatically managed so as to not exceed a predetermined limit. Specifically, after creation of information to be stored in a new recovery file, an automatic check is made to see if creation of the new recovery file will cause the space to exceed the limit. If so, at least one recovery file currently in the space is deleted. The new recovery file is automatically created, when the space occupied by existing recovery files becomes sufficiently small to accommodate the new file without exceeding the limit. The recovery file(s) deleted to make room for the new recovery file may be automatically identified in accordance with a user-specified policy. Such a policy may be used to automatically identify a subset of recovery files available for deletion, well ahead of time, i.e. prior to a need for deletion arises.

Abstract: A method and apparatus for creating a target database on a target platform based on a source database on a source platform is provided. A target database is created on the target platform based on data, metadata (for example, data in the system tablespace and control files), and external objects (for example, password files and externally stored tables) comprised within the source database. Data and metadata stored in tablespaces of the source database are converted to the format compatible with the target platform. The conversion of the data and metadata may be performed either at the source database or the target database. Redo information and undo information of the source database are not copied from the source database to the target database. Certain files, e.g., a password files, and links to externally stored object may be recreated on the target database.

Abstract: A system and method for enabling a second database instance to more quickly process a request to execute a database statement that has previously been executed by a first database instance is described. In one embodiment, the method involves sending the database statement from the first database instance to the second database instance, and generating by the second database instance one or more structures needed to prepare the statement for execution, such as a parse tree and an execution plan for the statement. If at some point in the future, the second database instance receives a request to execute the same statement, the above structures can be used for execution, thereby eliminating the need for one or more potentially time-consuming operations, such as generation of a parse tree or execution plan for the statement.

Abstract: Allocation of memory is optimized across multiple pools of memory, based on minimizing the time it takes to successfully retrieve a given data item from each of the multiple pools. First data is generated that indicates a hit rate per pool size for each of multiple memory pools. In an embodiment, the generating step includes continuously monitoring attempts to access, or retrieve a data item from, each of the memory pools. The first data is converted to second data that accounts for a cost of a miss with respect to each of the memory pools. In an embodiment, the second data accounts for the cost of a miss in terms of time. How much of the memory to allocate to each of the memory pools is determined, based on the second data. In an embodiment, the steps of converting and determining are automatically performed, on a periodic basis.

Abstract: Techniques for capturing samples of session activity in a database are provided. Session activity for active sessions is recorded at certain times over a time period. Accordingly, a sample of session activity is taken for sessions in a database.

Abstract: Techniques for self-diagnosing performance problems in a database are provided. The techniques include classifying one or more performance problems in a database system. One or more values for quantifying an impact of the one or more performance problems on the database system are then determined. The quantified values are determined based on the performance of operations in the database system. A performance problem based on the one or more quantified values is then determined. A solution for the performance problem is generated and may be outputted.

Abstract: Quantifying the impact of wasteful operations on a database system is provided. One or more operations that are determined to be wasteful are received. The impact of the wasteful operations on performance in a database may then be quantified. The database is monitored to determine when a wasteful operation is being performed. When a wasteful operation is detected, a time value is recorded of the time spent on processing the wasteful operation. The time value is stored and used to quantify an impact of a performance problem in a database. The time value may be stored and associated with other time values that are recorded for the same wasteful operation. Thus, the impact of wasteful operations that are performed and processed in a database may be determined.

Abstract: A method and system for implementing coalescing write IOs for an electronic and computerized system is disclosed. The electronic and computerized system has a buffer cache storing data blocks waiting for being written into a disk of the electronic and computerized system. Dirty data blocks with consecutive data block addresses in the buffer cache are coalesced and written to the disk together. Thus, the disk head movements for performing the write IOs are significantly reduced, thereby allowing the electronic and computerized system to maintain a high IO throughput and high peak performance with fewer disks.

Abstract: Described herein are techniques for global synchronization that under various scenarios eliminate or defer the acquisition of global locks. In many cases, the need to acquire global locks is eliminated, thereby saving the overhead attendant to processing global locks.

Abstract: A method and apparatus for determining a mapping of a database object to storage layers is provided. According to one aspect, a database server generates views that represent which components of each storage layer store parts of the object. The views are based on information that the database server automatically gathers from one or more vendor libraries. Each library implements a common API. Each storage layer is associated with a library. The database server passes the object's identifier to each library's implementation of a get-mapping routine of the API. A process that is associated with the storage layer that recognizes the object's identifier responds with the identity of one or more components of the storage layer that store one or more parts of the object. The database server recursively uses this information to obtain mappings between storage layer components and underlying storage layer components.

Abstract: Techniques are described herein for returning a repository to a prior state. The repository may be, for example a database, and the prior state may be, for example the consistent state that the database had at a particular point in time in the past. When a operator-caused error has been introduced to the database by changes made by an already-committed transaction, the techniques described herein may be used to recover from the error by returning the database to a point in time prior to the commit time of the transaction that introduced the error. The techniques involve the generation of “physical undo” information, and the use of the physical undo information in conjunction with physiological undo and physiological redo to efficiently return a repository to the prior state.

Abstract: A system is provided to manage retry communications between a client and a data source. The system includes a plurality of logical components that sequentially combine to form a communication path for a client communication. At least one of the components in the communication path is designated as a retry component. The retry component retries failed client communications for all of the components in the communication path.

Abstract: A method and apparatus for implementing segmented arrays in a database system. According to one embodiment of the invention, rather than allocating a contiguous block of memory for each array, the memory for storing at least selected arrays is broken into smaller pieces of memory referred to herein as memory segments. When the memory for an array is broken into memory segments, the array is referred to herein as a "segmented array." Each memory segment associated with a segmented array is divided into one or more memory areas, each of which represent an element of that array. The memory segments associated with a segmented array need not be contiguous. According to another aspect of the invention, the number of segments allocated for a segmented array can be increased or decreased during execution. According to yet another aspect of the invention, only some of the memory segments required to store a segmented array are initially allocated.