📝 Oracle SPARC Solaris (9 MCQs)

📖 Explanation: The relocation register holds an offset that is added to every logical address generated by a process. By applying this offset, the system converts the logical address into the correct physical location in RAM. Option B describes this behavior, making it the right choice. Options A, C, and D describe unrelated mechanisms such as limit checking, program counters, and cache protocols, which are not the function of the relocation register.

📖 Explanation: The limit register stores the maximum logical address a process is allowed to use. When the CPU generates an address, the hardware compares it to the limit value; any address above this threshold triggers a trap, preventing unauthorized memory access. This protection mechanism matches option C. Option A refers to encryption, which is unrelated. Option B describes the relocation register, not the limit register. Option D is about I/O, which the limit register does not manage.

📖 Explanation: Transient code is loaded into memory only when needed, temporarily increasing the operating system’s footprint. This expansion consumes space that would otherwise be available for user processes, effectively shrinking the number of free fixed partitions. Option B captures this effect. Option A is incorrect because Solaris can load code without rebooting. Option C ignores the dynamic nature of the relocation scheme. Option D misrepresents partition behavior, as partitions are not merged dynamically.

📖 Explanation: When a logical address exceeds the limit register value, the hardware generates a protection trap, preventing the memory operation. The operating system typically responds by sending a signal (such as SIGSEGV) or terminating the offending process. Therefore option B is correct. Option A ignores the protection check. Option C suggests silent failure, which does not occur. Option D incorrectly assumes the OS will adjust the limit register without explicit action.

📖 Explanation: The relocation‑limit hardware allows the OS to change the size of its code segment without moving other memory contents. By adjusting the limit register, the OS can shrink the driver’s region and return the freed portion to the pool of available memory within the same partition. Option B describes this dynamic resizing. Option A wastes space, Option C adds unnecessary I/O overhead, and Option D creates an extra partition, which the fixed‑partition model does not support.

📖 Explanation: The physical address is calculated by adding the relocation offset to the logical address: $\text{Physical} = \text{Relocation} + \text{Logical} = 0x1000 + 0x00A0 = 0x10A0$. Option A matches this result. Option B omits the offset, Option C misplaces the digits, and Option D adds an incorrect value. This arithmetic reflects how the dispatcher uses the relocation register during a context switch to map process addresses correctly.

📖 Explanation: Each process receives its own limit register that defines the highest address it may access within the shared partition. The hardware checks every generated address against this limit, generating a trap if a process exceeds its bounds, thus enforcing isolation even though the physical memory region is common. Option A correctly describes this mechanism. Option B is unrelated to memory protection. Option C would remove the necessary translation, and Option D suggests a software check that is less reliable than hardware enforcement.

📖 Explanation: To safely remove code, the OS must first reduce the limit register so that no new accesses can occur beyond the new boundary. It then copies any required state and finally adjusts the relocation register to reflect the new base address. This order prevents stray accesses during the transition. Option B follows this safe sequence. Option A clears registers before updating limits, risking illegal accesses. Options C and D introduce unnecessary reboots or disk writes, which are not part of the standard unload process.

📖 Explanation: In MFT, each partition has a predetermined size, so if a process does not exactly fill its partition, the leftover space becomes unusable, leading to external fragmentation. MVT, by allowing partitions to grow and shrink, can fit processes more tightly, reducing but not completely eliminating fragmentation. Therefore option A correctly captures the higher fragmentation in MFT. Option B is false because MVT can still have fragmentation. Option C ignores the structural differences, and Option D incorrectly claims MFT avoids fragmentation.