OBCP V4 Official Mock Exam Analysis (with Answers)
The OBCP V4 material runs a full 877 pages. Printed double-sided and offset-bound into a book on Taobao, it’s about 220 pages, totaling 23 RMB with free shipping in the Jiangsu-Zhejiang-Shanghai area. The book is very thick and packed with information—enough to study for a long time.
I worked through the official mock questions (if you haven’t done them yet, check the original first). I didn’t pass on the first round, retook it three more times and still didn’t pass, and in the end retook it eight rounds for the sake of one question. The OBCP exam isn’t entirely the same as real-world operations—you really do have to study the book carefully to pass.
What I’m sharing here are the mock questions publicly available on the OBCP V4 official site. I didn’t write the questions, and the official site doesn’t publish the answers. The answer analysis is based mainly on the tutorial content; for the occasional question where I couldn’t find corresponding content, it’s my personal guess.
Single-Choice Questions
1 LDC Routing
Answer analysis:
2 MEMSTORE Write Throttling Protection
Answer analysis:
3 Global Index
Answer analysis:
4 Operators for Distributed Execution
Answer analysis:
5 KVCache
Answer analysis:
6 ODP Deployment
Answer analysis:
7 HINT
Answer analysis:
8 OMS Data Migration
Answer analysis:
Structure migration handles DDL migration, while full migration only migrates the data.
9 obdumper
Answer analysis:
10 Read-Only Transactions
Answer analysis:
11 Session Views
12 Tenant Views
13 Global Index
Answer analysis:
14 Composite Index
Answer analysis:
15 Compaction Comparison
Answer analysis:
Good thing it’s single-choice—if it were a multiple-choice question, the answer would probably be CD.
16 Standby Tenant
Answer analysis:
This one is easy to get wrong; it differs a bit from operations in earlier versions.
17 OBServer Node Replacement
Answer analysis:
Replacing a node in an OB cluster is an online replacement.
Multiple-Choice Questions
18 Resource Units
Answer analysis:
The resource units in a tenant’s resource pools across different Zones can differ in size, but their quantity must be the same.
19 Replicated Tables
Answer analysis:
20 Table Locks
Answer analysis:
21 Index Matching
Answer analysis:
22 Daily Major Compaction
Answer analysis:
Major compaction can reduce the number of SSTables (because there are fewer versions).
23 OMS
Answer analysis:
24 JDBC Connection Properties
Answer analysis:
25 External Tables
Answer analysis:
26 Replacing a Node’s Disk
Answer analysis:
This one probably has the highest error rate and is also the most controversial.
Perhaps the question’s intent is to convey that since you’re just replacing a disk, you don’t need to remove the node, nor do you need to worry about the node going permanently offline. Just memorize the answer. It doesn’t affect the disk-replacement change steps in real operations.
27 Parallel Table Scan
Answer analysis:
28 Tenant Scaling
Answer analysis:
To check a node’s remaining resources, look at the gv$ob_servers view.
29 External Tables
Answer analysis:
The fields of an external table don’t have to correspond one-to-one with the fields of a table; what matters is the format definition.
30 Table Groups
Answer analysis:
A fairly difficult question.
Without a table group, the 9 partitions of these three partitioned tables would happen to have exactly one leader replica per node. With a table group, the leader replicas are constrained to nodes across three different zones.
31 Statistics
Answer analysis:
32 OB Logs
Answer analysis:
A trick question.
ilog only exists in versions before V4.
33 ODP High Availability
Answer analysis:
34 Paxos
Answer analysis:
True/False Questions
35 Standby Tenant
36 OB Log Levels
Answer analysis:
37 Resource Unit Specifications
Answer analysis:
38 Partitioned Tables
Answer analysis:
39 Load Balancing
Answer analysis:
Typically, an OB delivery requires load balancing to provide a layer-7 VIP for OCP and a layer-4 VIP for OBProxy.
40 External Tables
Answer analysis:
An external table is a file, so it’s definitely not writable.
41 obdumper
Answer analysis:
42 Buffer Tables
Answer analysis:
43 Standalone-Distributed Integration
Answer analysis:
The standalone edition of OB can be scaled out online into a distributed edition. And the other way around? Earlier versions could scale down from three replicas back to a single replica, but recent versions can’t anymore. You can only work around it via primary-standby tenants.
44 dbcat Tool
Answer analysis:
45 Configuration Items
Answer analysis:
OB’s configuration is the most chaotic (it merges the configuration approaches of Oracle and MySQL). What’s being discussed here are parameters. Many parameters under the sys tenant take effect across the entire cluster and are called cluster parameters. Under the sys tenant you can modify a user tenant’s parameters; a parameter under a user tenant only takes effect within its own tenant. You can only modify your own parameters.
46 Session Variables
Answer analysis:
Besides parameters, a user tenant also has variables, which borrow MySQL’s variable feature. They are further divided into global variables and session variables. Their effective mechanism and scope are consistent with MySQL.
47 ODP
Answer analysis:
ODP is the reverse proxy for an OB cluster. But an ODP cluster isn’t really a cluster—just a pile of ODP nodes stacked together. High availability and load balancing rely on the load balancing design above it (such as F5, A10, or NGINX, HAProxy, LVS, etc.).
48 explain
Answer analysis:
explain only generates an execution plan; it doesn’t execute the SQL. This differs from PG—there’s no explain analyze usage.
49 Major Compaction and Statistics
Answer analysis:
In V4, OB decoupled daily major compaction from statistics updates. The strategies for gathering statistics have grown increasingly rich and varied (automatic gathering, manual gathering, adaptive gathering, incremental gathering, etc.).
50 Log Stream
Answer analysis:
The log stream is something new in V4.x and isn’t easy to understand. You can refer to: Analysis of the OB V4 Log Stream Design
Summary
These are only mock questions, but you can see they all hew closely to concepts from the tutorial. The mock questions can be found via the “View Original” link below.
The only path to passing OBCP is to deeply understand the concepts and knowledge in the tutorial and practice on a real OB environment. Memorizing a question bank won’t get you far.
I’m happy to discuss OBCP V4 study, but I don’t have an OBCP V4 question bank—I can only discuss the content of the tutorial.