In Oracle Database architecture, what is the shared pool and what does it primarily store?

Introduction / Context:
The Oracle System Global Area, or SGA, is divided into several components that manage memory for different purposes. One of the most important components is the shared pool, which plays a key role in performance by caching parsed SQL statements, PL or SQL code, and data dictionary information. This question checks whether you understand the function of the shared pool and can distinguish it from storage components such as disks or user accounts.

Given Data / Assumptions:

• We are discussing Oracle Database architecture.
• The SGA resides in memory and is shared by all server processes.
• The shared pool is one of the logical subdivisions of the SGA.
• We want to know what is stored in the shared pool.

Concept / Approach:
The shared pool contains the library cache and data dictionary cache, among other structures. When a SQL statement is parsed and optimized, its parsed representation and execution plan can be stored in the library cache so that subsequent executions of the same statement can be reused, saving parsing time. PL or SQL packages and procedures are also cached. The data dictionary cache keeps metadata about tables, indexes, and users, reducing the need to query system tables repeatedly. A correct answer must mention memory, parsed SQL, PL or SQL, and data dictionary information.

Step-by-Step Solution:
Step 1: Recall that the shared pool is part of the SGA and resides entirely in memory. Step 2: Recall that it holds parsed SQL, PL or SQL code, and data dictionary entries to enable reuse and reduce parsing overhead. Step 3: Examine Option A, which states that it is a memory area in the SGA that stores parsed SQL statements, PL or SQL code, and data dictionary information for reuse. This matches the conceptual definition. Step 4: Examine Option B, which talks about a group of hard disks; this describes storage, not memory. Step 5: Examine Option C, which refers to a network card; this is hardware, not a memory structure. Step 6: Examine Option D, which describes user accounts; this is a security concept, not a memory pool. Step 7: Examine Option E, which describes directories and data files; again, this is storage layout, not SGA memory. Step 8: Conclude that Option A is the correct description.

Verification / Alternative check:
Oracle documentation for memory architecture describes the shared pool as containing the library cache and data dictionary cache. Examples show how enabling cursor sharing or using bind variables can increase the reuse of parsed statements in the shared pool and reduce parsing overhead. Monitoring tools also report shared pool usage and misses. None of this documentation suggests that the shared pool is related to disks, network cards, or user account groups.

Why Other Options Are Wrong:

• Option B is wrong because archived redo logs are stored on disk, not in SGA memory.
• Option C is wrong because a network card is physical hardware, not part of database memory.
• Option D is wrong because users can share roles and privileges, but this is not called the shared pool.
• Option E is wrong because directory placement is a storage design issue, not an SGA component.

Common Pitfalls:
A frequent pitfall is to size the shared pool too small, leading to frequent reloads and hard parses, which can hurt performance. Another mistake is to write applications that use many unique SQL literals instead of bind variables, which increases pressure on the shared pool. Monitoring shared pool statistics and tuning SQL usage patterns are important parts of performance tuning.

Final Answer:
The correct definition is Option A: It is a memory area in the System Global Area that stores parsed SQL statements, PL or SQL code, and data dictionary information for reuse.