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: 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, system, and computer program product is disclosed for interacting with a client supported by a client-side cache. Embodiments of a method, a system, and a computer program product are disclosed that retrieve a first snapshot, indicating a state of the database after a last database request by the client, associated with the client, determine any number of invalid cached results for the client based on the first snapshot, and transmit the any number of invalid cached results and a second snapshot, an update for the first snapshot.

Abstract: A method, system, and computer program product is disclosed for caching results in a client-side cache. Embodiments of a method, a system, and a computer program product are disclosed that associate a first snapshot of a database with a client that indicates a state of the database after a last database request by the client, and indicate any number of invalid cached results in the client cache for the client based upon the first snapshot. In some embodiments, the method further includes receiving a second snapshot that indicates a state of the database upon receipt of a database server request by the client, and updating the first snapshot with the second snapshot.

Abstract: A method, system, and computer program product forcost based analysis for data access in a database management system. In one approach, the method, system, and computer program productperforms identifying data to access, determining a first cost for direct I/O storage access and a second cost for cache access, performing a comparison between the first cost and the second cost, and accessing a first portion of identified data based upon the comparison.

Abstract: Techniques are provided for performing changes to a resource governed by a locking mechanism. An entity (such as a server instance in a database system cluster) requests permission to modify the resource. In response to the request, the entity receives a first lock on the resource, which grants permission to perform the change to the resource without making the change permanent. After receiving the first lock, the entity performs the change to a copy of the resource that resides in shared memory without making another copy of the resource. After performing the change and until receiving permission to make the change permanent, the entity prevents the change to the resource from becoming permanent. After performing the change, the entity receives a second lock on the resource, which grants the entity permission to make the change permanent. After receiving the second lock, the entity ceases to prevent the change to the resource from becoming permanent.

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 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: 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 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: Detecting an operating condition in a multi-server data storage system. One or more of the data storage servers are designated with a status within the cluster. The designating may be performed by at least one of the data storage servers. The status is encoded into log data having records that report changes to the primary data storage performed by the cluster of data storage servers. The log data is transmitted from the primary data storage to the standby data storage system. The standby data storage system determines an operating condition of the cluster of data storage servers based, at least in part, on the status.

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 lock manager system is provided that includes multiple distinct mechanisms for assigning resources to masters. Specifically, the lock manager system includes (1) one or more assignment mechanisms that do not take into account the affinity between nodes and objects (“affinity-independent assignment mechanisms”), and (3) one or more assignment mechanisms that do take into account the affinity between nodes and objects (“affinity-based assignment mechanisms”). At any given time, the assignment of any given resource to a master is governed by only one of the multiple assignment mechanisms employed by the system. Various techniques are described for determining which assignment mechanism to use with which resources.

Abstract: A method and apparatus is provided for maintaining data integrity. According to the method, a physical checksum calculation is performed on a block of data. After performing the physical checksum calculation, a logical check is performed on the data contained with the block of data. If the block of data passes the logical check, then the block of data may be written to nonvolatile memory. Thereafter, when the block of data is read from nonvolatile memory a physical checksum verification procedure is performed on the block of data to determine whether the block of data was corrupted after performing the logical check on the data contained with the block of data.

Abstract: Described herein are techniques for synchronizing access to resources in a multi node system by establishing a resource as a read-mostly resource based on one or more criteria, and allowing a node to acquire a shared lock, not granted by the master, on the read-mostly resource where no anti-lock exists for the resource.

Abstract: Techniques are provided for detecting lost writes so that data corruption can be avoided. According to one technique, lost writes are detected by comparing version numbers that are indicated in redo log entries with version numbers that are indicated in corresponding blocks in a standby database. According to one technique, which may be used in conjunction with the above technique, lost writes are detected by logging read operations that occur relative to a primary database, and comparing version numbers that are indicated in read log entries with version numbers that are indicated in corresponding blocks in a standby database. According to one technique, lost writes are detected by comparing, in response to read operations, (a) version numbers that are stored in a persistent in-memory cache with (b) version numbers that are indicated in corresponding blocks that are read from a primary database.

Abstract: Disclosed are methods, systems, and mediums for improving system utilization and throughput. In some embodiments, application requests received at a primary site are routed to a secondary site for processing when the requests are found to be suitable for processing at the secondary site.

Abstract: Provided herein is a mechanism that allows a given database system to access data blocks from another database system, where data blocks from the given database system and data blocks from the other database system have different sizes. According to an aspect of the present invention, a tablespace in the other database system contained the data blocks. The tablespace is detached from the other database system and integrated into the given database, which is capable of processing data stored in data blocks of different sizes.

Abstract: One embodiment of the present invention provides a resource scheduler for allocating a computer system resource, such as memory or mass storage, within a processor, to database management system (DBMS) processes. The resource scheduler operates according to resource plans and resource allocation methods. One or more plans may be configured and loaded with the DBMS. Each plan allocates the resource according to an associated resource allocation method. During operation of the DBMS, any or all of the active plans and resource allocation methods may be exchanged for alternate plans or resource allocation methods. In one embodiment of the invention the resource scheduler enforces a maximum active sessions resource allocation method in which system resources are allocated by limiting the number of active sessions allowed in groups of database processes grouped according to common execution requirements. A selected plan includes multiple process groups and/or sub-plans.

Abstract: Access to computer system resources is regulated by computing an estimated execution time for an operation which seeks to use the resources. Once computed, the estimated execution time is used to make decisions about granting the operation access to the computer system resources. Operations which have an estimated execution time greater than a user-supplied maximum estimated execution time allowable for the operation are denied access to the computer system resources. Operations which are denied access are rescheduled for later operation, queued, or aborted.