141. An open form can not be execute the call_form procedure if you chain of called forms has been initiated by another open form? - True
142. Explain about horizontal, Vertical tool bar canvas views? - Tool bar canvas views are used to create tool bars for individual windows. Horizontal tool bars are display at the top of a window, just under its menu bar. Vertical Tool bars are displayed along the left side of a window
143. What is the purpose of the product order option in the column property sheet? - To specify the order of individual group evaluation in a cross products.
144. What is the use of image_zoom built-in? - To manipulate images in image items.
145. How do you reference a parameter indirectly? - To indirectly reference a parameter use the NAME IN, COPY ‘built-ins to indirectly set and reference the parameters value’ Example name_in (’capital parameter my param’), Copy (’SURESH’,'Parameter my_param’)
146. What is a timer? - Timer is an “internal time clock” that you can programmatically create to perform an action each time the times.
147. What are the two phases of block coordination? - There are two phases of block coordination: the clear phase and the population phase. During, the clear phase, Oracle Forms navigates internally to the detail block and flushes the obsolete detail records. During the population phase, Oracle Forms issues a SELECT statement to repopulate the detail block with detail records associated with the new master record. These operations are accomplished through the execution of triggers.
148. What are Most Common types of Complex master-detail relationships? - There are three most common types of complex master-detail relationships: master with dependent details master with independent details detail with two masters
149. What is a text list? - The text list style list item appears as a rectangular box which displays the fixed number of values. When the text list contains values that can not be displayed, a vertical scroll bar appears, allowing the operator to view and select values that are not displayed.
150. What is term? - The term is terminal definition file that describes the terminal form which you are using r20run.
151. What is use of term? - The term file which key is correspond to which oracle report functions.
152. What is pop list? - The pop list style list item appears initially as a single field (similar to a text item field). When the operator selects the list icon, a list of available choices appears.
153. What is the maximum no of chars the parameter can store? - The maximum no of chars the parameter can store is only valid for char parameters, which can be up to 64K. No parameters default to 23 Bytes and Date parameter default to 7 Bytes.
154. What are the default extensions of the files created by library module? - The default file extensions indicate the library module type and storage format .pll - pl/sql library module binary
155. What are the Coordination Properties in a Master-Detail relationship? - The coordination properties are Deferred Auto-Query These Properties determine when the population phase of block coordination should occur.
156. How do you display console on a window? - The console includes the status line and message line, and is displayed at the bottom of the window to which it is assigned. To specify that the console should be displayed, set the console window form property to the name of any window in the form. To include the console, set console window to Null.
157. What are the different Parameter types? - Text ParametersData Parameters
158. State any three mouse events system variables? - System.mouse_button_pressedSystem.mouse_button_shift
159. What are the types of calculated columns available? - Summary, Formula, Placeholder column.
160. Explain about stacked canvas views? - Stacked canvas view is displayed in a window on top of, or “stacked” on the content canvas view assigned to that same window. Stacked canvas views obscure some part of the underlying content canvas view, and or often shown and hidden programmatically.
161. What are the built_ins used the display the LOV? - Show_lov List_values
162. What is the difference between SHOW_EDITOR and EDIT_TEXTITEM? - Show editor is the generic built-in which accepts any editor name and takes some input string and returns modified output string. Whereas the edit_textitem built-in needs the input focus to be in the text item before the built-in is executed.
163. What are the built-ins that are used to Attach an LOV programmatically to an item? - set_item_property get_item_property (by setting the LOV_NAME property)
164. How do you call other Oracle Products from Oracle Forms? - Run_product is a built-in, Used to invoke one of the supported oracle tools products and specifies the name of the document or module to be run. If the called product is unavailable at the time of the call, Oracle Forms returns a message to the operator.
165. What is the main diff. bet. Reports 2.0 & Reports 2.5? - Report 2.5 is object oriented.
166. What are the different file extensions that are created by oracle reports? - Rep file and Rdf file.
167. What is strip sources generate options? - Removes the source code from the library file and generates a library files that contains only pcode. The resulting file can be used for final deployment, but can not be subsequently edited in the designer.ex. f45gen module=old_lib.pll userid=scott/tiger strip_source YES output_file
168. What is the basic data structure that is required for creating an LOV? - Record Group.
169. What is the Maximum allowed length of Record group Column? - Record group column names cannot exceed 30 characters.
170. Which parameter can be used to set read level consistency across multiple queries? - Read only
171. What are the different types of Record Groups? - Query Record Groups NonQuery Record Groups State Record Groups
172. From which designation is it preferred to send the output to the printed? - Previewer
173. what are difference between post database commit and post-form commit? - Post-form commit fires once during the post and commit transactions process, after the database commit occurs. The post-form-commit trigger fires after inserts, updates and deletes have been posted to the database but before the transactions have been finalized in the issuing the command. The post-database-commit trigger fires after oracle forms issues the commit to finalized transactions.
174. What are the different display styles of list items? - Pop_list Text_list Combo box
175. Which of the above methods is the faster method? - performing the calculation in the query is faster.
176. With which function of summary item is the compute at options required? - percentage of total functions.
177. What are parameters? - Parameters provide a simple mechanism for defining and setting the values of inputs that are required by a form at startup. Form parameters are variables of type char, number, date that you define at design time.
178. What are the three types of user exits available? - Oracle Precompiler exits, Oracle call interface, NonOracle user exits.
179. How many windows in a form can have console? - Only one window in a form can display the console, and you cannot change the console assignment at runtime
180. If the maximum record retrieved property of the query is set to 10 then a summary value will be calculated? - Only for 10 records.
181. What are the two repeating frame always associated with matrix object? - One down repeating frame below one across repeating frame.
182. What are the master-detail triggers? - On-Check_delete_master, On_clear_details, On_populate_details
183. What are the different objects that you cannot copy or reference in object groups? - Objects of different modules Another object groups Individual block dependent items Program units.
184. What is an OLE? - Object Linking & Embedding provides you with the capability to integrate objects from many Windows applications into a single compound document creating integrated applications enables you to use the features form.
185. Is it possible to modify an external query in a report which contains it? - No.
186. Does a grouping done for objects in the layout editor affect the grouping done in the data model editor? - No.
187. Can a repeating frame be created without a data group as a base? - No
188. If a break order is set on a column would it affect columns which are under the column? - No
189. Is it possible to set a filter condition in a cross product group in matrix reports? - No
190. Do user parameters appear in the data modal editor in 2.5? - No
191. Can you pass data parameters to forms? - No
192. Is it possible to link two groups inside a cross products after the cross products group has been created? - no
193. What are the different modals of windows? - Modeless windows Modal windows
194. What are modal windows? - Modal windows are usually used as dialogs, and have restricted functionality compared to modeless windows. On some platforms for example operators cannot resize, scroll or iconify a modal window.
195. What are the different default triggers created when Master Deletes Property is set to Non-isolated? - Master Deletes Property Resulting Triggers: Non-Isolated (the default) On-Check-Delete-Master On-Clear-Details On-Populate-Details
196. What are the different default triggers created when Master Deletes Property is set to isolated? - Master Deletes Property Resulting Triggers: Isolated On-Clear-Details On-Populate-Details
197. What are the different default triggers created when Master Deletes Property is set to Cascade? - Master Deletes Property Resulting Triggers: Cascading On-Clear-Details On-Populate-Details Pre-delete
198. What is the diff. bet. setting up of parameters in reports 2.0 reports2.5? - LOVs can be attached to parameters in the reports 2.5 parameter form.
199. What are the difference between lov & list item? - Lov is a property where as list item is an item. A list item can have only one column, lov can have one or more columns.
200. What is the advantage of the library? - Libraries provide a convenient means of storing client-side program units and sharing them among multiple applications. Once you create a library, you can attach it to any other form, menu, or library modules. When you can call library program units from triggers menu items commands and user named routine, you write in the modules to which you have attach the library. When a library attaches another library, program units in the first library can reference program units in the attached library. Library support dynamic loading-that is library program units are loaded into an application only when needed. This can significantly reduce the run-time memory requirements of applications.
201. What is lexical reference? - How can it be created? - Lexical reference is place_holder for text that can be embedded in a SQL statements. A lexical reference can be created using & before the column or parameter name.
202. What is system.coordination_operation? - It represents the coordination causing event that occur on the master block in master-detail relation.
203. What is synchronize? - It is a terminal screen with the internal state of the form. It updates the screen display to reflect the information that oracle forms has in its internal representation of the screen.
204. What use of command line parameter cmd file? - It is a command line argument that allows you to specify a file that contain a set of arguments for r20run.
205. What is a Text_io Package? - It allows you to read and write information to a file in the file system.
206. What is forms_DDL? - Issues dynamic Sql statements at run time, including server side pl/SQl and DDL
207. How is link tool operation different bet. reports 2 & 2.5? - In Reports 2.0 the link tool has to be selected and then two fields to be linked are selected and the link is automatically created. In 2.5 the first field is selected and the link tool is then used to link the first field to the second field.
208. What are the different styles of activation of ole Objects? - In place activation, External activation
209. How do you reference a Parameter? - In Pl/SQL, You can reference and set the values of form parameters using bind variables syntax. Ex. PARAMETER name = ‘’ or :block.item = PARAMETER Parameter name
210. What is the difference between object embedding & linking in Oracle forms? - In Oracle forms, Embedded objects become part of the form module, and linked objects are references from a form module to a linked source file.
211. Name of the functions used to get/set canvas properties? - Get_view_property, Set_view_property
212. What are the built-ins that are used for setting the LOV properties at runtime? - get_lov_property set_lov_property
213. What are the built-ins used for processing rows? - Get_group_row_count(function) Get_group_selection_count(function) Get_group_selection(function) Reset_group_selection(procedure) Set_group_selection(procedure) Unset_group_selection(procedure)
214. What are built-ins used for Processing rows? - GET_GROUP_ROW_COUNT(function) GET_GROUP_SELECTION_COUNT(function) GET_GROUP_SELECTION(function) RESET_GROUP_SELECTION(procedure) SET_GROUP_SELECTION(procedure) UNSET_GROUP_SELECTION(procedure)
215. What are the built-in used for getting cell values? - Get_group_char_cell(function) Get_groupcell(function) Get_group_number_cell(function)
216. What are the built-ins used for Getting cell values? - GET_GROUP_CHAR_CELL (function) GET_GROUPCELL(function) GET_GROUP_NUMBET_CELL(function)
217. A tleast how many set of data must a data model have before a data model can be base on it? - Four
218. To execute row from being displayed that still use column in the row which property can be used? - Format trigger.
219. What are different types of modules available in oracle form? - Form module - a collection of objects and code routines Menu modules - a collection of menus and menu item commands that together make up an application menu library module - a collection of user named procedures, functions and packages that can be called from other modules in the application
220. What is the remove on exit property? - For a modeless window, it determines whether oracle forms hides the window automatically when the operators navigates to an item in the another window.
221. What is WHEN-Database-record trigger? - Fires when oracle forms first marks a record as an insert or an update. The trigger fires as soon as oracle forms determines through validation that the record should be processed by the next post or commit as an insert or update. Generally occurs only when the operators modifies the first item in the record, and after the operator attempts to navigate out of the item.
222. What is a difference between pre-select and pre-query? - Fires during the execute query and count query processing after oracle forms constructs the select statement to be issued, but before the statement is actually issued. The pre-query trigger fires just before oracle forms issues the select statement to the database after the operator as define the example records by entering the query criteria in enter query mode. Pre-query trigger fires before pre-select trigger.
223. What are built-ins associated with timers? - find_timer create_timer delete_timer
224. What are the built-ins used for finding object ID functions? - Find_group(function) Find_column(function)
225. What are the built-ins used for finding Object ID function? - FIND_GROUP(function) FIND_COLUMN(function)
226. Any attempt to navigate programmatically to disabled form in a call_form stack is allowed? - False
227. Use the Add_group_row procedure to add a row to a static record group 1. true or false? - False
228. Use the add_group_column function to add a column to record group that was created at a design time? - False
229. What are the various sub events a mouse double click event involves? - What are the various sub events a mouse double click event involves? - Double clicking the mouse consists of the mouse down, mouse up, mouse click, mouse down & mouse up events.
230. How can a break order be created on a column in an existing group? - What are the various sub events a mouse double click event involves? - By dragging the column outside the group.
231. What is the use of place holder column? - What are the various sub events a mouse double click event involves? - A placeholder column is used to hold calculated values at a specified place rather than allowing is to appear in the actual row where it has to appear.
232. What is the use of hidden column? - What are the various sub events a mouse double click event involves? - A hidden column is used to when a column has to embed into boilerplate text.
233. What is the use of break group? - What are the various sub events a mouse double click event involves? - A break group is used to display one record for one group ones. While multiple related records in other group can be displayed.
234. What is an anchoring object & what is its use? - What are the various sub events a mouse double click event involves? - An anchoring object is a print condition object which used to explicitly or implicitly anchor other objects to itself.
235. What are the various sub events a mouse double click event involves? - What are the various sub events a mouse double click event involves? - Double clicking the mouse consists of the mouse down, mouse up, mouse click, mouse down & mouse up events.
236. What are the default parameter that appear at run time in the parameter screen? - What are the various sub events a mouse double click event involves? - Destype and Desname.
237. What are the built-ins used for Creating and deleting groups? - CREATE-GROUP (function) CREATE_GROUP_FROM_QUERY(function) DELETE_GROUP(procedure)
238. What are different types of canvas views? - Content canvas views Stacked canvas views Horizontal toolbar vertical toolbar.
239. What are the different types of Delete details we can establish in Master-Details? - Cascade Isolate Non-isolate
240. What is relation between the window and canvas views? - Canvas views are the back ground objects on which you place the interface items (Text items), check boxes, radio groups etc.,) and boilerplate objects (boxes, lines, images etc.,) that operators interact with us they run your form . Each canvas views displayed in a window.
241. What is a User_exit? - Calls the user exit named in the user_exit_string. Invokes a 3Gl program by name which has been properly linked into your current oracle forms executable.
242. How is it possible to select generate a select set for the query in the query property sheet? - By using the tables/columns button and then specifying the table and the column names.
243. How can values be passed between precompiler exits & Oracle call interface? - By using the statement EXECIAFGET & EXECIAFPUT.
244. How can a square be drawn in the layout editor of the report writer? - By using the rectangle tool while pressing the (Constraint) key.
245. How can a text file be attached to a report while creating in the report writer? - By using the link file property in the layout boiler plate property sheet.
246. How can I message to passed to the user from reports? - By using SRW.MESSAGE function.
247. How is possible to restrict the user to a list of values while entering values for parameters? - By setting the Restrict To List property to true in the parameter property sheet.
248. How can a button be used in a report to give a drill down facility? - By setting the action associated with button to Execute pl/SQL option and using the SRW.Run_report function.
249. How can a cross product be created? - By selecting the cross products tool and drawing a new group surrounding the base group of the cross products.
250. What is a physical page? What is a logical page? - A physical page is a size of a page. That is output by the printer. The logical page is the size of one page of the actual report as seen in the Previewer.
251. What does the term panel refer to with regarda to pages? - A panel is the number of physical pages needed to print one logical page.
252. What is a master detail relationship? - A master detail relationship is an association between two base table blocks- a master block and a detail block. The relationship between the blocks reflects a primary key to foreign key relationship between the tables on which the blocks are based.
253. What is a library? - A library is a collection of subprograms including user named procedures, functions and packages.
254. How can a group in a cross products be visually distinguished from a group that does not form a cross product? - A group that forms part of a cross product will have a thicker border.
255. What is the frame & repeating frame? - A frame is a holder for a group of fields. A repeating frame is used to display a set of records when the number of records that are to displayed is not known before.
256. What is a combo box? - A combo box style list item combines the features found in list and text item. Unlike the pop list or the text list style list items, the combo box style list item will both display fixed values and accept one operator entered value.
257. What are three panes that appear in the run time pl/SQL interpreter? - Source pane, interpreter pane, navigator pane.
258. What are the two panes that Appear in the design time pl/SQL interpreter? - Source pane, interpreter pane
259. What are the two ways by which data can be generated for a parameters list of values? - Using static values, writing select statement.
260. What are the various methods of performing a calculation in a report? - Perform the calculation in the SQL statements itself, use a calculated / summary column in the data model.
261. What are the default extensions of the files created by menu module? - .mmb, .mmx
262. What are the default extensions of the files created by forms modules? - .fmb - form module binary .fmx - form module executable
263. To display the page number for each page on a report, what would be the source & logical page number or physical page number?
264. It is possible to use raw devices as data files and what is the advantages over file system files? - Yes. The advantages over file system files. I/O will be improved because Oracle is bypassing the kernel when writing to disk. Disk Corruption will decrease.
265. What are disadvantages of having raw devices? - We should depend on export/import utility for backup/recovery (fully reliable) The tar command cannot be used for physical file backup, instead we can use dd command which is less flexible and has limited recoveries.
266. What is the significance of having storage clause? - We can plan the storage for a table as how much initial extents are required, how much can be extended next, how much % should leave free for managing row updations etc.,
267. What is the use of INCTYPE option in EXP command? - Type export should be performed COMPLETE, CUMULATIVE, INCREMENTAL. List the sequence of events when a large transaction that exceeds beyond its optimal value when an entry wraps and causes the rollback segment to expand into a notion Completes. e. will be written.
268. What is the use of FILE option in IMP command? - The name of the file from which import should be performed.
269. What is a Shared SQL pool? - The data dictionary cache is stored in an area in SGA called the Shared SQL Pool. This will allow sharing of parsed SQL statements among concurrent users.
270. What is hot backup and how it can be taken? - Taking backup of archive log files when database is open. For this the ARCHIVELOG mode should be enabled. The following files need to be backed up. All data files. All Archive log, redo log files. All control files.
271. List the Optional Flexible Architecture (OFA) of Oracle database? How can we organize the tablespaces in Oracle database to have maximum performance?
1. SYSTEM - Data dictionary tables.
2. DATA - Standard operational tables.
3. DATA2- Static tables used for standard operations
4. INDEXES - Indexes for Standard operational tables.
5. INDEXES1 - Indexes of static tables used for standard operations.
6. TOOLS - Tools table.
7. TOOLS1 - Indexes for tools table.
8. RBS - Standard Operations Rollback Segments,
9. RBS1,RBS2 - Additional/Special Rollback segments.
10. TEMP - Temporary purpose tablespace
11. TEMP_USER - Temporary tablespace for users.
12. USERS - User tablespace.
272. How to implement the multiple control files for an existing database?
1. Shutdown the database
2. Copy one of the existing control file to new location
3. Edit Config ora file by adding new control filename
4. Restart the database.
273. What is advantage of having disk shadowing/ Mirroring? - Shadow set of disks save as a backup in the event of disk failure. In most Operating System if any disk failure occurs it automatically switches over to a working disk. Improved performance because most OS support volume shadowing can direct file I/O request to use the shadow set of files instead of the main set of files. This reduces I/O load on the main set of disks.
274. How will you force database to use particular rollback segment? - SET TRANSACTION USE ROLLBACK S
Operating system questions
Hardware, Unix/Linux, Windows interview questions
1. What are the basic functions of an operating system? - Operating system controls and coordinates the use of the hardware among the various applications programs for various uses. Operating system acts as resource allocator and manager. Since there are many possibly conflicting requests for resources the operating system must decide which requests are allocated resources to operating the computer system efficiently and fairly. Also operating system is control program which controls the user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of I/O devices.
2. Why paging is used? - Paging is solution to external fragmentation problem which is to permit the logical address space of a process to be noncontiguous, thus allowing a process to be allocating physical memory wherever the latter is available.
3. While running DOS on a PC, which command would be used to duplicate the entire diskette? diskcopy
4. What resources are used when a thread created? How do they differ from those when a process is created? - When a thread is created the threads does not require any new resources to execute the thread shares the resources like memory of the process to which they belong to. The benefit of code sharing is that it allows an application to have several different threads of activity all within the same address space. Whereas if a new process creation is very heavyweight because it always requires new address space to be created and even if they share the memory then the inter process communication is expensive when compared to the communication between the threads.
5. What is virtual memory? - Virtual memory is hardware technique where the system appears to have more memory that it actually does. This is done by time-sharing, the physical memory and storage parts of the memory one disk when they are not actively being used.
6. What is Throughput, Turnaround time, waiting time and Response time? - Throughput – number of processes that complete their execution per time unit. Turnaround time – amount of time to execute a particular process. Waiting time – amount of time a process has been waiting in the ready queue. Response time – amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment).
7. What is the state of the processor, when a process is waiting for some event to occur? - Waiting state
8. What is the important aspect of a real-time system or Mission Critical Systems? - A real time operating system has well defined fixed time constraints. Process must be done within the defined constraints or the system will fail. An example is the operating system for a flight control computer or an advanced jet airplane. Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. Real-Time systems may be either hard or soft real-time. Hard real-time: Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM), Conflicts with time-sharing systems, not supported by general-purpose operating systems. Soft real-time: Limited utility in industrial control of robotics, Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.
9. What is the difference between Hard and Soft real-time systems? - A hard real-time system guarantees that critical tasks complete on time. This goal requires that all delays in the system be bounded from the retrieval of the stored data to the time that it takes the operating system to finish any request made of it. A soft real time system where a critical real-time task gets priority over other tasks and retains that priority until it completes. As in hard real time systems kernel delays need to be bounded
10. What is the cause of thrashing? How does the system detect thrashing? Once it detects thrashing, what can the system do to eliminate this problem? - Thrashing is caused by under allocation of the minimum number of pages required by a process, forcing it to continuously page fault. The system can detect thrashing by evaluating the level of CPU utilization as compared to the level of multiprogramming. It can be eliminated by reducing the level of multiprogramming.
11. What is multi tasking, multi programming, multi threading? - Multi programming: Multiprogramming is the technique of running several programs at a time using timesharing. It allows a computer to do several things at the same time. Multiprogramming creates logical parallelism. The concept of multiprogramming is that the operating system keeps several jobs in memory simultaneously. The operating system selects a job from the job pool and starts executing a job, when that job needs to wait for any i/o operations the CPU is switched to another job. So the main idea here is that the CPU is never idle. Multi tasking: Multitasking is the logical extension of multiprogramming .The concept of multitasking is quite similar to multiprogramming but difference is that the switching between jobs occurs so frequently that the users can interact with each program while it is running. This concept is also known as time-sharing systems. A time-shared operating system uses CPU scheduling and multiprogramming to provide each user with a small portion of time-shared system. Multi threading: An application typically is implemented as a separate process with several threads of control. In some situations a single application may be required to perform several similar tasks for example a web server accepts client requests for web pages, images, sound, and so forth. A busy web server may have several of clients concurrently accessing it. If the web server ran as a traditional single-threaded process, it would be able to service only one client at a time. The amount of time that a client might have to wait for its request to be serviced could be enormous. So it is efficient to have one process that contains multiple threads to serve the same purpose. This approach would multithread the web-server process, the server would create a separate thread that would listen for client requests when a request was made rather than creating another process it would create another thread to service the request. To get the advantages like responsiveness, Resource sharing economy and utilization of multiprocessor architectures multithreading concept can be used.
12. What is hard disk and what is its purpose? - Hard disk is the secondary storage device, which holds the data in bulk, and it holds the data on the magnetic medium of the disk.Hard disks have a hard platter that holds the magnetic medium, the magnetic medium can be easily erased and rewritten, and a typical desktop machine will have a hard disk with a capacity of between 10 and 40 gigabytes. Data is stored onto the disk in the form of files.
13. What is fragmentation? Different types of fragmentation? - Fragmentation occurs in a dynamic memory allocation system when many of the free blocks are too small to satisfy any request. External Fragmentation: External Fragmentation happens when a dynamic memory allocation algorithm allocates some memory and a small piece is left over that cannot be effectively used. If too much external fragmentation occurs, the amount of usable memory is drastically reduced. Total memory space exists to satisfy a request, but it is not contiguous. Internal Fragmentation: Internal fragmentation is the space wasted inside of allocated memory blocks because of restriction on the allowed sizes of allocated blocks. Allocated memory may be slightly larger than requested memory; this size difference is memory internal to a partition, but not being used
14. What is DRAM? In which form does it store data? - DRAM is not the best, but it’s cheap, does the job, and is available almost everywhere you look. DRAM data resides in a cell made of a capacitor and a transistor. The capacitor tends to lose data unless it’s recharged every couple of milliseconds, and this recharging tends to slow down the performance of DRAM compared to speedier RAM types.
15. What is Dispatcher? - Dispatcher module gives control of the CPU to the process selected by the short-term scheduler; this involves: Switching context, Switching to user mode, Jumping to the proper location in the user program to restart that program, dispatch latency – time it takes for the dispatcher to stop one process and start another running.
16. What is CPU Scheduler? - Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them. CPU scheduling decisions may take place when a process: 1.Switches from running to waiting state. 2.Switches from running to ready state. 3.Switches from waiting to ready. 4.Terminates. Scheduling under 1 and 4 is non-preemptive. All other scheduling is preemptive.
17. What is Context Switch? - Switching the CPU to another process requires saving the state of the old process and loading the saved state for the new process. This task is known as a context switch. Context-switch time is pure overhead, because the system does no useful work while switching. Its speed varies from machine to machine, depending on the memory speed, the number of registers which must be copied, the existed of special instructions(such as a single instruction to load or store all registers).
18. What is cache memory? - Cache memory is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from larger memory.
19. What is a Safe State and what is its use in deadlock avoidance? - When a process requests an available resource, system must decide if immediate allocation leaves the system in a safe state. System is in safe state if there exists a safe sequence of all processes. Deadlock Avoidance: ensure that a system will never enter an unsafe state.
20. What is a Real-Time System? - A real time process is a process that must respond to the events within a certain time period. A real time operating system is an operating system that can run real time processes successfully
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