Laboratory work sharing resources. Sharing resources on Windows and Linux
Cross-Origin Resource Sharing (CORS) technology defines the way client web applications loaded into one domain interact with resources in another domain. The service's support for CORS technology allows you to build rich web applications on the client side and selectively provide Cross-origin access to your service resources.
This section provides information about cross-origin resource sharing (CORS) technology.
Each AllowedHeader line in a rule can contain a maximum of one "*" wildcard character. For example,
ExposeHeader element
Each ExposeHeader element specifies a header in the response that users can access from applications (for example, from a JavaScript XMLHttpRequest object). A list of typical service headers is in the “Typical request headers” section.
MaxAgeSeconds element
The MaxAgeSeconds element specifies the time, in seconds, that the browser can cache the response for a preflight request, as determined by the resource, HTTP method, and origin.
How the service evaluates the CORS configuration on the bucket
When the service receives a preflight request from the browser, it evaluates the CORS configuration for the bucket and uses the first CORSRule that matches the browser request it receives to resolve the Cross-origin request. In order for a rule to match a received request, the following conditions must be met.
- The request's Origin header must match the AllowedOrigin element.
- The request method (such as GET or PUT) or the Access-Control-Request-Method header in the case of a preflight OPTIONS request must be one of the AllowedMethod elements.
- Each title specified in the header Access-Control-Request-Headers in the preflight request, must match the AllowedHeader element.
Policies and control lists ACL access applicable when CORS technology is enabled on the bucket.
The main function of a LAN is to share resources. Even if users have different computer configurations, access to information and resources is equally necessary for everyone. LAN can provide sharing to the following computer hardware:
Hard disks. General use of hard disks means access from one computer to data on another computer and vice versa. Every user network defines, which folders, files, printers and other resources on his computer can be accessed by others. This means that no one is forced to completely open up their drive for public use. In addition, disk sharing allows for centralized archiving and recovery of stored data, which saves time and costs on storage media.
CD-ROM drives. Although CD-ROM drives are increasingly included in the delivery of new computers; there may not be many of them on the network. You can share these devices among members working group and use them to install programs, copying files, watching videos and much more. Installing programs and reading files from CD-ROM drive occurs faster than from floppy disks or magnetic tape. Eliminating the need to install CD-ROM drives on each network workstation saves money, and users who have never had a CD-ROM drive will be able to access the information supplied by the disks.
Files. You can share not only applications, but also files. Files are stored in folders on hard drives workstations. Local area network OS allows you to choose specific folders for general access, while access to any folder can be limited. It should be remembered that only some types of files, such as databases, can be accessed simultaneously for both reading and writing.
Printers. Even though printers have become significantly cheaper than they used to be, it hardly makes sense to equip each workstation with its own printing device. Installing one or two shared printers per workgroup, such as a laser for general printing and a color for presentations, will save money and allow everyone to print when needed. Using a local area network OS, you can easily organize access to your printer for several colleagues, and, if necessary, it is also easy to terminate this access.
When using a resource, there are two ways to control access to it. You can protect a resource with a password, which is called resource level control, or specify a list of users who can access the resource, this is called user level control. At any time you can open access to your resources or close it. The user decides whether to grant other members of the workgroup access to files on his computer or not.
Basic LAN topologies
The computers that are part of the LAN can be located in the most random manner on the territory where the computer network is being created. It should be noted that for the method of accessing the transmission medium and methods of network management, it is not indifferent to how the subscriber computers are located. Therefore, it makes sense to talk about LAN topology.
LAN topology is an averaged geometric diagram of connections of network nodes.
Computer network topologies can be very different, but for local area networks only three are typical: ring, bus, star-shaped .
Sometimes the terms are used to simplify things - ring, tire And star. One should not think that the types of topologies considered are an ideal ring, an ideal straight line, or a star.
Any computer network can be considered as a collection of nodes.
Node - any device directly connected to the network transmission medium.
Topology averages the connection pattern of network nodes. So, an ellipse, a closed curve, and a closed broken line belong to the ring topology, and an open broken line belongs to the bus topology.
Ring topology provides for the connection of network nodes in a closed curve - a transmission medium cable (Fig. 2). The output of one network node is connected to the input of another. Information is transmitted along the ring from node to node. Each intermediate node between the transmitter and the receiver relays the sent message. The receiving node recognizes and receives only messages addressed to it.
Ring topology is ideal for networks that occupy a relatively small space. There is no central node, which increases the reliability of the network. Relaying information allows you to use any type of cable as a transmission medium.
Rice. 2. Ring topology network
Consistent discipline in servicing the nodes of such a network reduces its performance, and the failure of one of the nodes violates the integrity of the ring and requires special measures to be taken to preserve the information transmission path.
Due to the difficulties with cabling, most LAN manufacturers design networks with a pure ring topology. Instead, a special central hub is used that implements a ring topology in a network with a star-shaped cable layout.
Bus topology - one of the simplest (Fig. 3). It is associated with the use of coaxial cable as a transmission medium. Data from the transmitting network node is distributed along the bus in both directions. Intermediate nodes do not broadcast incoming messages. Information arrives at all nodes, but only the one to which it is addressed receives the message. The service discipline is parallel.
Rice. 3. Bus topology network.
This ensures high performance of a LAN with a bus topology. The network is easy to expand and configure, as well as adapt to various systems. The bus topology network is resistant to possible failures of individual nodes.
Computers in networks with a bus topology have equal access to the backbone cable at any time. Before sending data to another computer, you need to check that the cable is free. This check is performed at the logical level. In order to prevent collisions, merging functions are carried out at the same level (as at highway entrances).
The disadvantage of this topology is that all network traffic depends on the backbone cable. If the cable breaks at any point or when another node is connected, the entire network will stop functioning. However, this is usually the cheapest option as it only requires a common cable to connect the nodes.
Bus topology networks are the most common today. It should be noted that they are short in length and do not allow the use of different types of cable within the same network.
Star topology is based on the concept of a central node, called a hub (Fig. 4), to which peripheral nodes are connected. Each peripheral node has its own separate communication line with the hub. All information is transmitted through a central node, which relays, switches and routes information flows in the network.
Rice. 4. Star network
The star topology greatly simplifies the interaction of LAN nodes with each other and allows the use of simpler network adapters. At the same time, the performance of a LAN with a star topology depends entirely on the central node.
The advantage of such networks is that each computer's cable is protected from damage by any other cable. If the connection of any computer is disrupted or its cable is broken, then only this computer will lose connection with the network, the remaining computers will maintain a connection to each other through the hub. From the point of view of network reliability, this type of topology is the best.
The disadvantages of a star topology occur when very small networks are used. The cost of a central hub can be quite expensive. Depending on the brand of the hub and the number of connections provided, it can reach several thousand dollars.
In real computer networks, more complex topologies can be used, representing in some cases combinations of those considered.
The choice of a particular topology is determined by the scope of the LAN, the geographical location of its nodes and the size of the network as a whole.
Under resources PC will be understood as any of the following elements:
Logical drives, including drives on CD-ROM, ZIP, DVD and other similar devices;
Directories (folders) with or without subdirectories (subfolders), as well as the files contained in them;
Devices connected to the PC: printers, modems, etc.
A resource that is accessible only from the PC on which it is located is called local. A PC resource available to other computers on the network is called shared or network (common, shared). A local resource can be made shared, and, conversely, a shared resource can be returned to the status of local, i.e., access to it can be denied to other network users.
The creation of shared network resources and access to them are provided by special network operating systems . Basic networking opportunities Network operating systems allow you to copy files from one PC on the network to another, and from one computer on the network to process data (enter, edit, delete, search) located on another. For some network operating systems, you can also run a program located in the memory of one computer, which will operate on data stored on another PC.
Typically one or more powerful PCs are used (dedicated servers) which make their resources available for sharing online. The shared access system operates on the principle of sharing the operating time of the host computer.
Depending on the network resources used in hierarchical networks, the following types of servers are distinguished.
File server. In this case, shared files and/or shared programs are located on the server. In this case, only a small (client) part of the programs is located on the workstations, requiring insignificant resources. Programs that allow this mode of operation are called programs with the ability to be installed on a network. The requirements for server power and network bandwidth for this method of use are determined by the number of simultaneously working workstations and the nature of the programs used.
Database server. The server hosts a database that can be replenished from various workstations and/or provide information upon requests from a workstation. Two fundamentally different modes of processing requests from a workstation or editing records in a database are possible:
Database records are sequentially sent from the server to the workstation, where the actual records are filtered and the necessary ones are selected;
The server selects itself necessary records from the database (implements the request) and sends them to the workstation.
In the second case, the network load and requirements for workstations are reduced, but the requirements for server computing power sharply increase. However, this is the most efficient way to process requests. The specified method of satisfying requests from workstations is called mode client-server, it will be implemented special means working with modern network databases data. In systems client-server data processing is divided between two entities: client and server. The client is the task work station, user. He can generate a request for the server: read a file, search for a record, etc. The server is the device or computer that processes the request. He is responsible for storing data, organizing access to this data and transferring data to the client.
Print server. A fairly powerful printer is connected to a low-power computer, which can print information from several workstations at once. Software organizes a queue of print jobs and also identifies printed information special pages(bookmarks) that separate printed materials from different users.
Mail server. The server stores information sent and received both over the local network and externally (for example, via a modem). At any time convenient for him, the user can view the information received in his name or send via mail server my.
Topologies
Topology– geometric display of relationships in the network. According to the topology, LANs are divided into: common bus, ring, star, etc.
Star topology
Star network topology– a type of network where each terminal is connected to central station(Fig. 2).
This topology is taken from the field of large electronic computers. Here the file server is located in the “center”.
Network advantages:
Cable damage is a problem for one specific computer and does not generally affect the operation of the network;
The connection is simple, since the workstation only needs to connect to the server;
Protection mechanisms against unauthorized access are optimal;
High data transfer speed from workstation to server, since both PCs are directly connected to each other.
Flaws:
While data transfer from workstation to server (and vice versa) is fast, data transfer speeds between individual workstations are slow;
The power of the entire network depends on the capabilities of the server; if it is insufficiently equipped or poorly configured, it will be a brake on the entire system;
Communication between individual workstations is impossible without the help of a server.
Figure 2. Star topology
A topology with a server in the center is practically not implemented, since in this case the server must have many network adapters, workstations are connected to a concentrator (hub).
Ring topology
Ring network– a type of network in which each terminal is connected to two other adjacent terminals on the ring.
In this case, all workstations and the server are connected to each other via a ring through which information is sent along with the recipient's address. Workstations receive the relevant data by analyzing the address of the sent message (Fig. 3).
Rice. 3. Ring topology
Advantages of a ring-type network:
Flaws:
Data transfer time increases in proportion to the number of computers connected in a ring;
Each workstation is involved in data transmission; the failure of one station can paralyze the entire network if special transition connections are not used;
When connecting new workstations, the network should be turned off briefly.
Bus topology
Such a network is similar to a central line to which a server and individual workstations are connected. The bus topology was widespread in previous years, which can primarily be explained by the low cable requirements (Fig. 4).
Rice. 4. Bus topology
Advantages of the bus topology:
Low cable costs;
Workstations can be installed or disconnected at any time without interrupting the operation of the entire network;
Workstations can communicate with each other without the help of a server.
Flaws:
When a cable breaks, the entire section of the network from the point of break fails;
Possibility of unauthorized connection to the network, since to increase the number of workstations there is no need to interrupt the network.
Combined LAN structure
Along with the well-known topologies of computer networks: ring, star and bus, a combined one is also used in practice. It is formed mainly in the form of combinations of the above-mentioned computer network topologies (Fig. 5).
Figure 5. Combined structure
Computer networks with a combined structure are used where direct application of basic network structures in their pure form is not possible. To connect a large number of workstations, use network amplifiers and/or switches. A switch that simultaneously has amplifier functions is called an active hub.
A passive hub is usually used as a splitter. It doesn't need an amplifier. The prerequisite for connecting a passive hub is that the maximum possible distance to the workstation should not exceed several tens of meters.
Seven-level LAN model
The LAN must have a reliable and fast system data transmission, the cost of which should be less than the cost of connected workstations. In other words, the cost of a transmitted unit of information should be significantly lower than the cost of processing information in workstations. Based on this, the LAN, as a system of distributed resources, should be based on the following principles:
Unified transmission medium;
Unified management method;
Unified protocols;
Flexible modular organization;
Information and software compatibility.
International Organization for Standardization (ISO), based on experience multi-machine systems, which was accumulated in different countries, put forward the concept of open systems architecture - reference model, used in the development of international standards.
Based on this model computer network appears as a distributed computing environment that includes a large number of different hardware and software. Vertically given environment is represented by a number of logical levels, each of which is assigned one of the network tasks. Horizontally The information and computing environment is divided into local parts (open systems) that meet the requirements and standards of the open systems structure.
Part open system, performing a certain function and being part of a particular level is called object.
The rules by which objects of the same level interact are called a protocol.
Protocol– a set of rules and procedures governing data exchange.
Protocols define the order in which information is exchanged between network objects. They allow communicating workstations to make calls to each other, interpret data, handle error conditions, and perform many other functions. various functions. The essence of protocols lies in regulated exchanges of precisely specified commands and responses to them (for example, assignment physical level communication - transfer of blocks of data between two devices connected to the same physical medium).
The data transfer protocol requires the following information:
Synchronization. Synchronization refers to the mechanism for recognizing the beginning of a data block and its end.
Initialization. Initialization refers to the establishment of a connection between interacting partners. Provided that the receiver and transmitter are using the same protocol, synchronization is established automatically.
Blocking. Blocking means partitioning transmitted information into strictly defined data blocks maximum length(including identification marks of the beginning of the block and its end).
Addressing. Addressing provides identification of the various equipment in use that exchange information with each other during communication.
Error detection. Error detection refers to setting and checking control bits.
Block numbering. The current block numbering allows you to identify erroneously transmitted or lost information.
Data flow control. Data flow control serves to distribute and synchronize information flows. So, for example, if there is not enough space in the data device buffer or the data is not processed quickly enough in peripheral devices, messages and/or requests accumulate.
Recovery methods. After the data transmission process is interrupted, recovery methods are used to return to a certain position to retransmit the information.
Access permission. Distribution, control and management of data access restrictions are the responsibility of the access permission clause (for example, “transmit only” or “receive only”).
Each level is divided into two parts:
Service Specification;
Protocol specification.
The service specification defines what does a level do, and the protocol specification is how he does it. Moreover, each specific level can have more than one protocol.
Big number levels used in the model provides decomposition of the information and computing process into simple components. In turn, an increase in the number of levels makes it necessary to include additional connections in accordance with additional protocols and interfaces. Interfaces (macro commands, programs) depend on the capabilities of the OS used.
The International Organization for Standardization has proposed seven-level model, which corresponds to and program structure(Fig. 6).
Figure 6. Control levels and LAN protocols
Let's look at the functions performed by each layer of software.
1. Physical– carries out both connections to and disconnection from a physical channel, channel control, and also determines the data transfer rate and network topology.
2. Duct– frames the transmitted arrays of information with auxiliary symbols and controls the transmitted data. In a LAN, the transmitted information is divided into several packets or frames. Each packet contains source and destination addresses, as well as error detection.
3. Network – determines the route for transmitting information between networks (PC), provides error processing, as well as data flow management. The main task of the network layer is data routing (data transfer between networks). Special devices – routers determine for which network this or that message is intended, and forward this parcel to given network. To identify a subscriber within the network, a Node Address. To determine the path of data transmission between networks, routers are built Routing Tables, containing the sequence of data transmission through routers. Each route contains the address of the destination network, the address of the next router, and the cost of transmitting data along this route. When estimating the cost, the number of intermediate routers, the time required for data transmission, and the monetary cost of data transmission over the communication line can be taken into account. To build route tables, they most often use either m vector method either with static method. When choosing the optimal route, dynamic or static methods. On network level It is possible to use one of two packet transmission procedures:
datagram– when part of a message or packet is independently delivered to the recipient along different routes determined by the prevailing dynamics in the network. Moreover, each packet includes a full header with the recipient's address. The procedures for controlling the transmission of such packets over the network are called datagram services;
virtual connections – when the transmission route of the entire message from the sender to the recipient is established using a special service packet - a connection request. In this case, a route is selected for this packet and, if the recipient responds positively to the connection, it is assigned to all subsequent traffic (message flow in the data network) and the number of the corresponding virtual channel (connection) is obtained for further use its other packets of the same message. Packets that are transmitted over the same virtual circuit are not independent and therefore include a shortened header including serial number packet belonging to one message. Disadvantages compared to a datagram are complexity in implementation, increased overhead costs caused by establishing and releasing messages.
4. Transport– connects lower levels (physical, channel, network) with upper levels, which are being implemented software. This level separates the means of generating data on the network from the means of transmitting it. Here the information is divided according to a certain length and the destination address is specified. The transport layer allows multiplexing of transmitted messages or connections. Message multiplexing allows you to transmit messages simultaneously over several communication lines, and connection multiplexing allows you to transmit several messages for different connections in one package.
5. Session– at this level, communication sessions between two interacting users are managed (determines the beginning and end of a communication session: normal or emergency; determines the time, duration and mode of a communication session; determines synchronization points for intermediate control and recovery during data transfer; restores a connection after errors in communication session time without data loss).
6. Executive – controls the presentation of data in the form required by the user program, generation and interpretation of process interaction, data encoding/decoding, including data compression and decompression. Workstations can use various operating systems: DOS, UNIX, OS/2. Each of them has its own file system, their own formats for storing and processing data. The task this level is the conversion of data when transmitting information into a format that is used in information system. When receiving data, this data representation layer performs the inverse transformation. Thus, it becomes possible to organize data exchange between stations that use different operating systems. Data presentation formats may differ in the following ways:
Bit order and symbol size in bits;
Byte order;
Representation and character encoding;
File structure and syntax.
Compressing or packing data reduces data transfer time. Encoding of transmitted information protects it from interception.
7. Applied– he is in charge of applied network programs, serving files, as well as performing computational, information retrieval work, logical transformations of information, transmission mail messages and so on. The main task of this level is to ensure user-friendly interface for the user.
At different levels, various units of information are exchanged: bits, frames, packets, session messages, user messages.
Data transfer protocols
There are different networks various protocols data exchange. The most widespread is the specific implementation of access methods in networks Ethernet type, Arcnet and Token-Ring.
Access method in Ethernet networks
This access method, developed by Xerox in 1975, is the most popular. It provides high data transfer speed and reliability.
A message sent by one workstation is received simultaneously by all others. The message includes the address of the destination station and the address of the sending station. The station to which the message is intended receives it, the others ignore it.
The access method in Ethernet networks is a multiple access method with carrier listening and collision resolution (CSMA/CD - Carrier Sense Multiple Access/Collision Detection)
Before transmission begins, the workstation determines whether the channel is free or busy. If the channel is free, the station begins transmitting. Ethernet does not exclude the possibility of simultaneous transmission of messages by two or more stations. The equipment automatically recognizes such conflicts, called collisions. After detecting a conflict, stations delay transmission for a while, then resume transmission.
In reality, conflicts lead to a decrease in network speed only if there are at least 80-100 stations operating in the network.
Access method in Arcnet networks
This access method was developed by Datapoint Corp. It has also become widespread mainly due to the fact that Arcnet equipment is cheaper than Ethernet equipment or Token-Ring. Arcnet technology is used in local networks with a star topology. One of the computers creates a special token (a special type of message), which is sequentially transmitted from one computer to another.
If a station wishes to send a message to another station, it must wait for the token and append a message to it, complete with the address of the sender and the address of the destination station. When the packet reaches the destination station, the message will be “unhooked” from the token and transmitted to the station.
Access method in Token-Ring networks
In this tutorial we will look at additional features standard edition of MS Project 2002. The main topic of the lesson is managing multiple projects. You'll learn how to avoid conflicts when allocating resources between projects and how to schedule related projects. In addition, you will learn to simultaneously analyze data from several projects, combining them into general idea or report.
You'll learn convenient techniques for working with groups of project files and learn how to save a workspace, create project databases, and prepare templates for creating new project plans from them. In addition, you will learn how to configure MS Project 2002 Consultant and how to work with software add-ons.
Simultaneous management of several projects within an organization is complicated by the fact that employees and material resources must be assigned to tasks so that the assignments of some projects do not conflict with others. For example, you cannot allocate an employee to a task on July 1 if on that day he is already involved in another project.
The successful implementation of projects in an organization depends on the consistency of resource planning. To ensure this consistency, MS Project includes the ability to use a single list of resources stored in separate file, - the so-called Resource Pool.
Setting up a resource pool
To coordinate resource planning, you need to create regular file project in *.mpp format and place all data about resources in it. Projects with plans are then created, and they indicate that the planning will use resources from the first file, which in MS Project terms is called a resource pool. As an example, we created a file pool pool. mpp and two files with plans where pool resources should be used - 1.mpp and 2.mpp.
To define a resource pool for use in a project plan, you need to open both the plan file and the pool file (in our case, open the 1.mpp and pool.mpp files). Then, being in the plan file window, you should select the menu command Tools\u003e Resource Sharing\u003e Share Resources (Tools\u003e Shared Resources> Access to resources). This will open the definition dialog box. public access to resources, in which the parameters for working with the pool are configured (Fig. 23.1).
To enable resource pool mode, you must select the Use resources radio button in this dialog box, and then select the project file name from the drop-down list. For example, for file 1.mpp we specified the file pool.mpp as the resource pool.
Rice. 23.1. Configuring Resource Pool Usage
NOTE
The file that uses resources from the pool is called a pool client (sharer). A pool client cannot be a resource pool for another project plan.
When a client connects to the pool, data synchronization begins: all resources are copied to the client file, and you can work with them as with regular project resources - edit their properties, add and delete, etc. When assigning resources to plan tasks, information about the assignments copied to the pool file.
It may happen that after editing the data in the client file, the composition and properties of the client resources will differ from the composition and properties of the pool resources. In this case, when synchronizing the client and the pool, the program needs to determine which file has priority. If the pool has the advantage, then the client's data is updated in accordance with the pool data, but if the client has the advantage, then the pool is updated in accordance with the client's data.
ATTENTION
Pool resource assignment data is always transferred from the client file to the pool file, regardless of benefit.
To determine which file will take precedence in case of conflicts, you must select either the Pool takes precedence or the Sharer takes precedence radio button in the dialog box. Typically the first radio button is selected because it eliminates the possibility of adding inconsistent or random changes. Often the pool is located on network drive and a limited number of people have the right to change it. In this case, if you do not have rights to change the pool, only the first option is suitable for you.
To change the pool usage settings later, you need to open this dialog box again. By selecting the Use own resources checkbox, you can choose not to use the pool. After this, only those resources that are assigned to its tasks will remain in the project, and the rest will be deleted.
You can also change the settings for the relative advantage of files in conflicts. For example, if you edited resource data in a pool client file and want it to be retained in the pool when synchronized, you would open a dialog box and select the Sharer takes precedence radio button. After synchronization, when the changed data has been saved in the pool, you need to reopen the dialog box and select the Pool takes precedence radio button so that the pool again takes precedence in the future.
Planning using a pool
After the client and pool resource lists are synchronized, resources are allocated to tasks in the client file in the usual way. In this case, MS Project takes into account data on resource assignments in other projects. Let's look at working with one resource in two projects using the example of our files 1.mpp and 2.mpp, which use pool resources pool.mpp. In the first project, we created a task lasting 5 days, called it 1_1 and allocated A.A. Ivanov for its execution. Then in the second project we also created a task with a duration of 5 days and called it 2_1. Both projects start on the same day, and therefore this task is scheduled at the same time as task 1_1.
Now let's try to allocate a resource to task 2_1. For this we will use dialog box assignment of resources (see section “Replacing resources”), which opens using the button of the same name standard panel tools or the menu command Tools\u003e Assign Resources (Tools\u003e Assign resources). To select only the employees available at the time we need, check the Available to work checkbox and enter 40 hours in the counter, since our task lasts that long. The resource Ivanov A.A., already assigned to a task in another project at this time, immediately disappears from the list, and the program does not offer to assign him to the task (Fig. 23.2).
If the project has automatic resource leveling mode enabled (see section “Analysis and Leveling of Resource Loading”), then MS Project will automatically reschedule a task to another time if the resource assigned to its execution is already allocated at that time to the execution of another task in another project, connected to the pool.
You can try to enable this mode in the 2.mpp file and assign Ivanov A.A. to complete task 2_1. The task will automatically be moved forward a week, that is, to the end of task 1_1 in the project plan 1.mpp. If you disable automatic resource leveling and then open the Resource Sheet view, you will see that MS Project has determined that Ivanov A.A. has exceeded availability.
How does the program determine what time a resource is loaded in other projects? The point is that summary data about the resource load of all clients in the pool is contained in the pool, and when it is open, this information is available.
To view resource utilization information and take it into account when planning, you need to open the Resource Usage view in the pool client file (the pool file must also be open in MS Project). For each resource, it lists all the tasks in which it is involved. To determine which project a task belongs to, you must add a Project column to the table.
Rice. 23.2. The program determines who can be assigned to perform the task
This column can refer to either resources or tasks. In file 2.mpp (Fig. 23.3), we added it to the table, and it shows that the resources belong to the poo1.mpp project, and task 1_1, in which A.A. Ivanov is involved. - to project 1.mpp. We are looking at the data in the 2.mpp file, but the diagram shows that it stores data related to loading the resource in the 1.mpp file. The list also displays unassigned tasks in all clients of the pool, for example, task 2_1 from file 2.mpp is not assigned
Rice. 23.3. Data about resource loading in other projects - pool clients is displayed in each project if the pool is loaded
Pool usage
When you open a project plan file that uses resources from a pool, a dialog box appears that allows you to open the pool file along with the file (Figure 23.4).
Rice. 23.4. Dialog box to open the pool file along with the project plan
The dialog box contains two radio buttons, and if you select the top one, MS Project will load the pool file along with the project plan. If you select the bottom switch, the program will open only the file with the project plan.
If you open a project file for scheduling, it is better to always select the top radio button, because you can only view resource load in other projects when the pool is open. Moreover, only when open file changes can be made to the pool.
NOTE
When opening the pool using the top switch shown in Fig. 23.4, the pool opens in read mode.
Collaboration with the pool
If one file is edited by several users at the same time, this will lead to a conflict when saving it, and the data of one of the users will most likely be lost. Therefore, MS Project does not allow the resource pool to be opened for writing by two users at the same time.
When opening a pool file, the program asks whether to open the file in write or read-only mode. If you select write mode, then no one except you will be able to make changes to the pool file. If you open a pool file for reading, you can make changes to it only if it is not open for writing by another user.
To open a file in reading mode, use the top switch of the dialog box shown in Fig. 23.5, and for opening in recording mode - average.
If the pool is opened in write mode, then the data in it can be edited in the usual way. If you opened the pool for reading, then it needs to be updated after you change the project plan, otherwise data about new resource assignments will not get into the pool and will not be available in other files - clients of the pool. To update the pool taking into account design data, use the menu command Tools > Resource Sharing > Update Resource Pool (Tools > Shared resources > Update resource pool). This command is only available when the pool file is open for reading. If the pool file is open for writing, it is updated automatically and this menu command is not used.
When you select this command, the MS Project menu opens the pool file for writing, updates the pool data, and then opens it for reading again. This mode allows several users to make changes to the pool alternately.
To update the properties of resources in a pool when it is read-only, you need to update them in the pool client file, and then in the pool usage settings (see Figure 23.1) specify that the client has priority. In this case, the changed resource information will be saved in the pool after it is updated.
If you have a read-only pool and are working on a plan, remember that someone else can update the pool in the same way as described above. For example, when you opened the plan file, Petrov was free on Monday. You assigned him a full load task for that day and continued working on the plan without updating the pool. At this time, another project manager also assigned Petrov a task with a full load for Monday, but updated the pool. In this case, your assignment, once stored in the pool, will exceed Petrov's availability.
To eliminate potential conflicts while working on a project plan, after you finish planning, you should refresh the pool (that is, save your plan data to it), and then refresh the pool screen (that is, transfer the most recent data from the pool to your plan).
The pool screen is updated using the menu command Tools > Resource Sharing > Refresh Resource Pool (Tools > Shared Resources > Refresh Resource Pool Screen).
When you select this command, the MS Project menu re-opens the pool file, and changes made to it by other users are available to you. Typically, after updating the pool screen, changes occur in the plan: some resources become overloaded or project costs change. To find changes, you can save a version of the plan before updating the pool screen and then, using an automated comparison (see the section “MS Project Files”), compare it with the one obtained after updating the pool screen.
Under resources PC will be understood as any of the following elements:
- · logical drives, including CD-ROM drives, DVDs and other similar devices;
- · directories (folders) with or without subdirectories (subfolders), as well as the files contained in them;
- · devices connected to the PC: printers, modems, etc.
A resource that is accessible only from the PC on which it is located is called local. A PC resource available to other computers on the network is called shared or network (common, shared). A local resource can be made shared and, conversely, a shared resource can be returned to the status of local, i.e., access to it can be denied to other network users.
The creation of shared network resources and access to them are provided by special network operating systems. The basic networking capabilities of network operating systems allow you to process data from one network computer (enter, edit, copy, delete, search) located on another.
Typically one or more powerful PCs are used (dedicated servers) which make their resources available for sharing online. The shared access system operates on the principle of sharing the operating time of the host computer.
Depending on the network resources used in hierarchical networks There are the following types of servers.
1. File server.
In this case, shared files and/or shared programs are located on the server. At the same time, only a small (client) part of the programs is located on workstations, requiring insignificant resources. Programs that allow this mode of operation are called programs with the ability to be installed on a network. Server power requirements and bandwidth Networks with this method of use are determined by the number of simultaneously working workstations and the nature of the programs used.
2. Database server.
The server hosts a database that can be replenished from various workstations and/or provide information upon requests from a workstation. Two fundamentally different modes of processing requests from a workstation or editing records in a database are possible:
- · database records are sequentially sent from the server to the workstation, where the actual records are filtered and the necessary ones are selected;
- · the server itself selects the necessary records from the database (implements the request) and sends them to the workstation.
In the second case, the network load and requirements for workstations are reduced, but the requirements for computing power server. However, this is the most efficient way to process requests. The specified method of satisfying requests from workstations is called mode client-server, it is implemented by special tools for working with modern network databases. In systems client-server data processing is divided between two entities: client and server. A client is a task, a workstation, a user. He can generate a request for the server: read a file, search for a record, etc. The server is the device or computer that processes the request. He is responsible for storing data, organizing access to this data and transferring data to the client.
3. Print server.
A fairly powerful printer is connected to a low-power computer, which can print information from several workstations at once. The software organizes a queue of print jobs and also identifies printed information with special pages (bookmarks) that separate printed materials from different users.
4. Mail server.
The server stores information sent and received both over the local network and externally (for example, via a modem). At any time convenient for him, the user can view the information received in his name or send his information through the mail server.
Access to network resources local area network
To work in a local network it is used system folder network, which displays all available LAN resources.
To display a list of all computers included in a workgroup, you must click on the "Display workgroup computers" item in the "Network Tasks" command panel of the "Network Neighborhood" window.
By double-clicking on any of the remote computers in the "Network Neighborhood" window, you can see which of its resources are available for work. These remote resources can be worked with in the same way as files local disks in the Explorer program.
Managing network access to disks, folders, and printers
In order for other LAN users to access your PC resources, such as a printer, logical drives, folders, and files, you must open network access to these resources and set user rights to work with each of these resources.