databases Online Quiz - 42

Oracle's data dictionary provides several views for tracking privileges. USER_COL_PRIVS displays column-level privileges granted to the current user, while USER_COL_PRIVS_MADE shows column privileges the user granted to others. USER_TAB_PRIVS and USER_TAB_PRIVS_MADE are for table-level privileges.

In SQL, NULL represents an unknown value and cannot be compared using the = operator. Any comparison with NULL returns NULL (unknown), never true or false. To check for NULL values, you must use the IS NULL or IS NOT NULL operators. The statement WHERE DEPARTMENT_ID IS NULL would correctly find employees without a department assignment.

Data validation after extraction requires multiple checks to ensure data quality. NULL check identifies missing values, MetaData Check verifies schema compliance, Duplicate Check removes redundant records, and Invalid Check identifies values that don't meet business rules or data type constraints. All four validations are essential components of ETL data quality processes.

In DataStage Oracle OCI stage, the Array Size property controls the number of rows written in each batch to the database. Increasing this value reduces network round trips between DataStage and Oracle by buffering more rows before sending them, which significantly improves write performance for bulk operations. This is a performance tuning technique specifically for write operations, not reads.

Datasets in DataStage/Informatica parallel jobs improve performance by enabling parallel processing of data pipelines. Unlike sequential files, datasets partition data across multiple nodes allowing simultaneous processing, which reduces overall job execution time. The dataset format is optimized for parallel read/write operations and eliminates serialization bottlenecks.

In the context of IBM InfoSphere DataStage (extending from the previous DataStage question), the default cache size is 128MB. This can be configured by administrators under the tunables settings. Other options represent non-default sizes that must be manually configured for specific performance requirements.

IBM InfoSphere DataStage Director provides three standard views to monitor and manage jobs: Job View, Log View, and Status View. These views allow users to monitor statuses, view execution logs, and manage jobs. "Run view" is not a standard view in DataStage Director.

Subject-based addressing in messaging systems routes messages based on a topic or subject line rather than explicit source or destination addresses. This facilitates decoupled communication between data producers and data consumers. Other options are incorrect because they imply direct identification or addressing between specific producers and consumers.

The subject Invoice.Ny.TN matches these patterns: Invoice...> (Invoice with two wildcards before >), Invoice..> (Invoice with one wildcard before >), and Invoice. (Invoice with wildcard, assuming implicit queue match). That's 4 matching patterns. The patterns >, *.>, and I?.> do not match because the subject has more segments. Invoice. (without wildcard) doesn't match either.

The default queue limit policy is Discard none (A), which means the queue will accept unlimited messages and will not discard any messages regardless of queue size. This is the default behavior in most messaging systems to prevent message loss. Option B (Discard first), Option C (Discard New), and Option D (Discard last) are all overflow policies that must be explicitly configured, not the default.

When a queue reaches capacity and a new event arrives, the 'discard new' policy means the newest (youngest) event is discarded while keeping existing events. 'Discard last' and 'discard first' refer to removing the oldest or newest event respectively, while 'discard none' means the queue grows unbounded. The typo in option D ('Discrd') doesn't change its meaning.

In certified messaging, when a scheduler fails, the replacement scheduler waits for the completion time interval (20 seconds) before reassigning incomplete tasks. This delay ensures the original scheduler had sufficient time to complete the task before declaring it failed. Immediate reassignment would cause duplicate processing, while 'never happens' is incorrect because certified messaging guarantees delivery.

The monitor callback function in TIBCO Rendezvous receives the number of active elements in the queue as its argument. This allows the monitor to track queue occupancy and take action when thresholds are reached. Activation interval and heartbeat interval are timer parameters, not monitor callback arguments.

PARAM_MISMATCH error occurs when the activation interval parameter differs between the sender and receiver in TIBCO Rendezvous. This parameter must match for both parties to establish consistent communication expectations. 'Active goal' and 'lost interval' are different parameter types that don't cause this specific error.

By default, when the TIBCO Rendezvous daemon (rvd) is started automatically by a client application rather than with the -permanent option, it automatically terminates after 15 minutes of inactivity (having no active clients).

The default TCP port for TIBCO Rendezvous Routing Daemon (rvrd) is 7500. This is the standard port used for Rendezvous network communications. Ports 7600, 7680, and 7504 are used for other TIBCO services or are non-standard configurations.

Present perfect 'Mohan has come' correctly uses 'has' for third-person singular subjects. 'Mohan have comes' wrongly pairs singular subject with plural auxiliary and adds unnecessary 's', 'Mohan is come' incorrectly uses present continuous, and 'Mohan was come' misuses past tense.

The _LOCAL.SUB subject name indicates local communication within the same daemon and service. When programs use subjects prefixed with _LOCAL., they communicate through the same daemon instance and same service without going through the network. Different daemons or services would use different subject naming conventions.

TibrvEvent requires a queue (to manage event dispatching) and a callback function (to handle the event). Listener and transport are associated with TibrvTx and TibrvListener, not basic event objects. The queue schedules the callback execution, making both essential for event processing.