Database Administration and SQL Best Practices

Parallel degree depends on many factors beyond just leaf block count: system configuration, optimizer cost calculations, table size, and available CPU resources. A fixed rule of 5000 blocks = degree 2 doesn't exist. The parallel degree is determined by the optimizer based on total cost, not just block count.

Similar to the previous question, there is no fixed rule that 50000-250000 leaf blocks automatically equals degree 16 parallelism. The degree of parallelism is calculated by the optimizer based on multiple factors including system resources, operation cost, and initialization parameters, not just block count ranges.

The NOLOGGING clause instructs the database to write minimal logging information to the redo log files during operations like bulk inserts or index creation. This significantly reduces redo log generation and speeds up the operation.

Procedures such as EXPORT_TABLE_STATS in database optimizer packages are specifically provided to export optimizer statistics of an existing table for transfer or backup purposes.

If serial execution completes in less than 50% of the window time, parallelism should NOT be considered because the operation is already fast enough. Parallelism adds overhead and complexity - it's only worthwhile when operations are slow. The statement claims it SHOULD be considered, which is wrong.

The primary purpose of code comments is to explain the 'why' and context of complex code, rather than documenting every individual change (which is the job of version control histories like git). The statement describes commit messages or changelogs.

The PRIMARY goal of logging is debugging and troubleshooting during development and testing, not production performance monitoring. In production, you use tools like AWR, ASH, and SQL Trace for performance issues. The statement incorrectly claims production performance identification is the PRIMARY goal of logging.

Hints should not be used for full table scans because the optimizer already chooses full table scans when appropriate based on statistics. Forcing parallelism via hints can degrade performance if the operation doesn't actually benefit from it. The optimizer automatically determines when parallel execution is beneficial.

In an EXPLAIN PLAN for a parallel DML operation, the PX COORDINATOR appears ABOVE the DML operation, not below. The coordinator orchestrates parallel execution servers that perform the actual DML. The plan shows the coordinator as the parent operation managing the parallel workers.

Standard code comment lines are documentation for human readers and do not dictate or contain runtime properties about compiler or framework parallelism, which are handled via configuration files or compilation flags.

Comments are never mandatory for SQL code to execute. While adding comments is a good practice for code maintainability, UNION and UNION ALL operators work perfectly fine without comments. The statement incorrectly suggests comments are necessary.

UNION and UNION ALL are fundamental SQL operations with legitimate use cases. UNION eliminates duplicates and UNION ALL keeps all rows including duplicates. They should not be categorically avoided - the choice depends on whether you need duplicate elimination.

Under BT and general corporate security guidelines, sharing user accounts is strictly prohibited to maintain accountability and audit trails. Account sharing violates standard security policies, making the statement false.

In data warehousing, you want to MINIMIZE read/write operations, not maximize them. Excessive I/O operations slow down performance. The goal is to optimize query performance by reducing unnecessary data movement. The statement suggests the opposite of best practice.

You don't necessarily need to check if a table exists before creating it. You can use CREATE TABLE IF NOT EXISTS syntax, or let the database return an error if it exists. While checking is good practice in some contexts, it's not mandatory. The statement incorrectly presents it as a requirement.

Logging elapsed time for SQL statements is a performance monitoring best practice, but it's not mandatory for every SQL statement in PL/SQL. This would add overhead and isn't always necessary. The statement is overly prescriptive.

Comments explaining business logic are good practice but not required for SQL to execute. SQL is a declarative language that functions perfectly without comments. The statement incorrectly presents comments as mandatory.