Pass the MongoDB Certified DBA Associate C100DBA Questions and answers with Dumpstech

The --fork option starts mongod in daemon mode so the server process continues in the background. When --fork is used, MongoDB requires diagnostic output to be redirected through a logging destination such as --logpath or --syslog; the process cannot simply detach while continuing to use the normal foreground output stream. Option C supplies both --fork and a valid log path, while leaving the other server settings at their normal defaults unless they are configured elsewhere. Option A explicitly sets the default port but does not satisfy the logging requirement associated with --fork. Option B treats the literal word default as a filesystem path and does not provide the required log destination. Option D uses an unsupported --default switch. In production, MongoDB packages commonly use service managers such as systemd, and a configuration file is usually preferred over manually launching mongod with a long list of command-line options. Nevertheless, among the commands shown, C is the one that correctly daemonizes the server process and provides the logging configuration required for a successful fork.

Study Guide reference/topic:MongoDB Architecture and Core Operations - mongod startup, background execution, logging, and server configuration.

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MongoDB exposes server parameters that can be configured through the parameter framework. Among the choices, --setParameter is the option specifically designed to set a server parameter on the mongod command line, using syntax such as mongod --setParameter < name > = < value > . A configuration file can also contain a setParameter section, but --config by itself merely tells mongod which configuration file to load; it is not the parameter-setting mechanism identified by the question. Connection-string options control how clients connect and cannot be used to configure arbitrary server runtime parameters. Option D is also incorrect because the server must already be running for mongosh to issue administrative commands. A technical nuance is important: parameters that support modification while the process is already running are changed with the administrative setParameter command, for example db.adminCommand({setParameter:1, ...}). Such runtime changes may not persist across a restart unless the value is also configured for startup. Given the options provided and the exam wording, --setParameter is the intended method, so A is correct.

Study Guide reference/topic:MongoDB Architecture and Core Operations - server parameters, --setParameter, configuration files, and runtime administration.

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db.currentOp() reports information about operations that are currently in progress and accepts a filter document to restrict the output. The ns field in current-operation information identifies the namespace, typically in database.collection form. The regular expression /^qa\./ therefore matches namespaces beginning with qa., which isolates operations targeting collections in the qa database. Option C correctly supplies that namespace expression as a filter argument to db.currentOp(). Options A and B use a nonexistent db.listOps interface. Option D incorrectly treats ns as though it were a property or method chained from db.currentOp; filtering belongs inside the argument document. On current MongoDB versions, administrators are encouraged to use the $currentOp aggregation stage for more powerful filtering and composition, but the legacy helper remains the interface being tested here. Once the problematic operation is identified, the DBA can inspect details such as operation type, namespace, duration, waiting state, and client information before deciding whether additional action such as optimization or termination is justified. Thus C is the correct command.

Study Guide reference/topic:Performance Monitoring and Tuning - active operations, namespaces, long-running operation diagnostics, and currentOp.

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Queryable Encryption is designed for client-side protection of sensitive fields while preserving supported query capabilities over encrypted values. With this model, appropriately configured client drivers encrypt selected fields before data is transmitted to the MongoDB server and decrypt authorized results on the client side. That architecture is well suited to highly sensitive PII such as government identification numbers, dates of birth, or regulated demographic information because the database server stores encrypted field values rather than plaintext for those protected fields. The Encrypted Storage Engine, option A, protects database files at rest but the server can still process decrypted data internally. TLS/SSL, option B, protects data while it is moving across the network, not the application field values from the database server itself. Role-Based Access Control, option C, restricts which authenticated principals can perform actions but does not itself cryptographically protect the field contents. Queryable Encryption complements, rather than replaces, TLS, authentication, authorization, auditing, and storage encryption. For the specific requirement of client-side encryption of sensitive application data, option D is the correct MongoDB feature.

Study Guide reference/topic:Security, Networking, and Encryption - Queryable Encryption, client-side encryption, sensitive fields, and key management.

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The result depends on how the two concurrent operations interleave at document _id:3. MongoDB guarantees atomicity for each individual document write, but updateMany() is not atomic across the complete set of matching documents. Other operations can run between its per-document modifications. findAndModify also returns the pre-modification version of the selected document by default unless configured to return the updated version. If findAndModify reaches the X-phone first, it observes quantity 850, returns that pre-image, and sets the value to 1250. The concurrent updateMany() can subsequently reach the same document and set it to 0, producing option B. In another valid interleaving, updateMany() first sets the X-phone quantity to 0. findAndModify then selects that document, returns the pre-image showing 0, and sets the value to 1250. Because updateMany() has already processed that document, the final value can remain 1250, producing option D. Options A and C do not correctly reflect the default pre-image return behavior together with the possible per-document interleavings. Therefore B and D are both valid outcomes.

Study Guide reference/topic:MongoDB Architecture and Core Operations - single-document atomicity, concurrent writes, findAndModify, and updateMany.

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