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ClearCase Server Processes
ClearCase is a distributed application. Many of its operations involve several host
computers and several server processes on each host. This section introduces the
ClearCase server processes.
For the most part, these servers do not need to be explicitly configured, started,
stopped, or managed. The information in this section is intended to help you
understand status and error messages that may be generated by these servers, to access
server logs, and to get a better idea of the role each server process plays in a ClearCase
network.
Two server processes— albd_server and admin_server—run on every host that has
been configured to support local VOBs and views, regardless of whether any VOBs or
views have been created on the host. Other server processes are started as necessary to
manage any VOBs and views that reside on the host.
Note: ClearCase LT clients cannot be configured with support for local VOBs or views.
No ClearCase server processes run on a ClearCase LT client host or on a ClearCase host
that has been configured with no support for local VOBs and views.
ClearCase 服务器进程
Clearcase是一个分布式的应用软件。它的大多数的操作涉及到一些服务器主机和在这些主机上的一些进程。这部分介绍ClearCase的服务器进程。
对于大多数部分，这些服务不需要显示的被配置，启动，停止和管理。本章节的知识更有效的帮助你理解可能由这些服务引起的状态和错误的消息，访问服务日志，和得到更好的概念对于每个服务在ClearCase网络中所扮演的角色。
两个服务器进程- albd_server 和admin_server-运行在已经被配置在支持本地VOBs和Views的每个主机上，而不管是否有任何VOBs或者Views已经被创建在主机上。其他的服务进程被作为管理任何VOBs和Views的必要而启动长驻在主机上。
注意：ClearCase LT客户端对于支持本地的VOBs或者Views不能被配置，没有ClearCase的服务进程运行在ClearCase LT的客户主机或者在不支持本地的VOBs或者Views已经被配置的ClearCase的主机上。
albd_server
The albd_server handles a variety of tasks on hosts configured to support local VOBs
and views:
_ Starting and stopping other ClearCase services as needed.
_ Setting up network communications between ClearCase clients and servers.
_ Managing execution of tasks run by the ClearCase scheduler.
Chapter 1 - ClearCase Network Planning and Administration 9
_ Responding to requests for registry information on a ClearCase registry server
host.
_ Responding to requests for licenses on a ClearCase license server host.
(ClearCase LT does not use the albd_server in this way.)
_ On UNIX hosts, responding to load-balancing queries from a remote clearmake
process. (This feature is not supported on ClearCase LT.)
When you start ClearCase, the albd_server starts first, and runs with one of the
following user identities:
_ root on UNIX
_ The built-in LocalSystem identity on ClearCase LT on Windows
_ A specially created privileged user account on ClearCase on Windows
When you stop ClearCase, the albd_server stops all ClearCase services on the host and
then exits.
Note: On a ClearCase LT client or a ClearCase client configured without support for
local VOBs and views, the albd_server is not installed, and there are no other
ClearCase services to stop or start.
When a client program wants to access a service (a VOB or view server, for example)
on a ClearCase server host, it uses a remote procedure call (RPC) to send a request to
the albd_server process on that host. The albd_server starts the requested service if it
is not already started, then issues a response telling the client the service’s port number.
Thereafter, the client communicates directly with the specific service, without
involving the albd_server.
ClearCase services started by the albd_server generally run with the identity of the
resource (VOB or view) owner on UNIX and with the identity of the albd_server on
Windows.
Port Assignment
The albd_server listens for RPCs on a well-known port (port 371) that has been
reserved for it by the Internet Assigned Numbers Authority. ClearCase installation
verifies that no other service uses this port for UDP or TCP communications. If a
conflict is detected, we recommend that you modify the conflicting service to use
another port. If you cannot reconfigure or remove the conflicting service, you must
configure the albd_server to use a different UDP port.
_ On UNIX, edit the local host’s services database and/or the NIS services map.
10 Administrator’s Guide: Rational ClearCase and Rational ClearCase LT
_ On Windows, create the appropriate entry in the
file%SystemRoot%/System32/drivers/etc/services. (If there is no entry for the
albd_server in this file, it will use port 371.)
Note: All albd_server processes in a community must use the same port number. If you
change the albd_server port assignment on any ClearCase host, you must change it on
every ClearCase host.
The albd_server reads configuration file albd.conf during startup to determine which
services to provide. Do not modify this file.
Albd_server
Albe_server在配置成支持本地Vobs和Views的主机上运行了多种任务。
l 当需要的时候启动和停止其他的ClearCase服务
l 在ClearCase的服务器和客户机间设置网络通信。
l 管理ClearCase的调度程序任务的执行
l 响应ClearCase的注册服务主机上的注册信息的请求
l 响应ClearCase的License主机上的License请求（ClearCase LT不使用Albd_Server用这种方式）
l 在Unix主机，响应远程的ClearMake进程的查询装载平衡（ClearCase LT不支持这种功能）
当你启动ClearCase时，albe_Server首先被启动，并且以下面一种的用户身份运行。
l 在Unix上的root
l 在Windows上ClearCase LT的内置本地系统身份
l 在Windows上ClearCase特别创建的一个有特殊权利的用户帐号
当你停止ClearCase，Albd_Server服务停止所有在主机上的其他的服务，然后退出。
注意：如果ClearCase LT客户端或者ClearCase客户端的配置不支持本地VOBs和Views，那么这个服务将不被安装，因此就没有其他服务可以停止或启动。
当一个客户端程序想访问ClearCase服务器主机上的一个服务（例如，VOBs或者Views），它使用远程程序调用ＲＰＣ对主机上的Albd_Server发送一个请求，如果这个请求服务没有运行，那么Albd_Server将启动它，然后给客户端一个回应，告诉它服务的端口号，其后，客户端就可以直接和特定服务进行通信，而不用涉及Albd_Server。
ClearCase服务被Albd_Server启动，通常的又被在Unix主机上资源（VOBs和Views）的所有者的身份和在Windows的Albd_Serveer身份运行。
端口分配
Albd_Server监听RPC在一个众所周知的371端口，这个端口已经被Internet Assigned Numbers Authority.所保留，ClearCase安装检验这个端口没有被其他的服务以UDP或者TCP通讯的方式使用，如果冲突一旦被发觉，我们建议你使用冲突的服务使用其他端口号，如果你不能重新配置这个服务或者移除冲突的服务，你就得去配置Aldb_Server使用其他的UDP端口。
l 在Unix机，编辑本地服务器的数据和/或NIS服务匹配
l 在Windows机，创建一个合适的条目在 file%SystemRoot%/System32/drivers/etc/services.
（如果对于Albd_Server在文件中没有条目，那么它就使用371端口）
注意：所有的Aldb_Server的进程在通讯中必须使用相同的端口号。如果你改变了端口的配置在任何一台ClearCase主机上，你就得改变它在每一个主机的端口配置。Aldb_Server在启动的时候读取 albd.conf这个配置文件，用来决定提供哪些服务。不要修改此文件。
admin_server
The ClearCase administration server (admin_server) is invoked as needed by the
host’s albd_server process. This short-lived server performs miscellaneous
administrative support functions:
_ Retrieving server log files for display by the getlog command and the ClearCase
Administration Console.
_ Retrieving and changing the local host’s ClearCase properties when requested by
the ClearCase Administration Console.
_ Moving registry files and reconfiguring clients if the host is a backup registry
server.
Admin_Server
ClearCase的管理服务当需要的时候由主机上的albd_Server进程调用。这个短期的服务完成各种各样的管理支持功能。
l 显示回收服务的日志文件通过getlog命令在ClearCase的管理控制台
l 回收和改变本地主机的ClearCase属性当ClearCase管理控制台发出请求的时候
l 移动注册文件和重新配置客户端如果主机是备份注册服务器
credmap_server
The credentials mapping server credmap_server runs on any ClearCase host that is
configured to support local VOBs and views. This server handles credentials mapping
in environments where users access a common set of VOBs and views from both UNIX
and Windows computers. For more information, see Credentials Mapping on page 56.
credmap——server
凭证映射服务器运行在被配置成支持本地VOBs和Views的任何ClearCase主机上。这个服务操作凭证在那些用户访问在Unix和Windows机器上的一个VOBs和Views的通用设置的环境。更多的信息，请参考凭证映射在56页。
view_server
A view_server is a long-lived process that manages activity in a particular view. A
view_server is started by the host’s albd_server process whenever a client requests
access to a view. A view_server remains active until it is terminated by a cleartool
endview –server command, a system shutdown, or an operating system command
that terminates the view_server process.
When it begins execution, a view_server reads configuration information from
the .view file in the view-storage directory. Values in this file are established by
mkview, chview, and similar commands. Do not modify this file with a text editor.
View_Server
一个View_Server是一个常驻进程，它管理者活动在指定的View。无论什么时候当客户端请求访问View的时候，View_Server就被主机的albd_Server进程启动。它一直保持激活状态除非通过一个服务器命令cleartool endview关闭它，或者系统关闭了，或者一个操作系统的命令关闭了view_Server这个进程。
当它开始执行，view_Server读取配置信息从在view-storage目录下的.view文件。信息值通过mkview，chview和类似的命令在这个文件中创建，不要修改这个文件用文本编辑器。
vob_server
For each VOB, a long-lived vob_server process runs on the VOB host. The vob_server
manipulates data in the VOB’s storage pools in response to requests from client
processes.
The vob_server is the only process that ever creates or deletes VOB data containers;
only the VOB owner or a privileged user can modify VOB data containers and storage
pools. For more information, see The VOB Storage Directory on page 105.
A vob_server process is started as needed by albd_server. It remains active until any
of the following events occur:
_ The VOB is removed with the rmvob command.
_ ClearCase is stopped on the VOB server host.
_ The VOB server host is shut down and restarted.
When it begins execution, the vob_server reads configuration information from the file
vob_server.conf in the VOB storage directory. Values in this file are established by the
vob_snapshot_setup utility and other commands. Do not modify this file.
Vob_Server
对于每个VOB，一个常驻vob_server的进程运行在VOB的服务器上。它操纵数据在VOB’s
存储池用来响应客户端进程的请求。Vob_server是一个唯一永远创建或者删除VOB数据的容器，只有VOB的属主或者有特殊权限的用户才能修改VOB数据容器和存储池。有关更多的VOB存储目录信息在105页。
Vob_server进程当需要的时候被albd_server启动，它保持激活状态直道任何以下的事件发生：
l VOB通过rmvob命令删除了
l 在VOB服务器上的ClearCase被停止了运行
l VOB服务器关闭和重启
当它开始运行的时候，vob_server读取VOB storage目录下的vob_server.conf文件的配置信息。信息值通过vob_snapshot_setup和其他命令在这个文件中有效的创建。不要修改这个文件。
db_server
A host’s db_server processes manage VOB database transactions on that host in
response to requests from client programs. Because client programs cannot access VOB
databases directly, they must send database transaction requests to a db_server process
when they need to create, read, or modify VOB data or metadata.
Each db_server process services a single client at a time, but can operate on any
number of VOBs. A client establishes a connection to a db_server with the help of the
albd_server on the VOB host. If necessary, the albd_server starts a new db_server
process to handle a request. The connection is broken when the client exits or becomes
idle (stops requesting database transactions for an extended period). At that point, the
db_server becomes available for use by another client. After a period of idleness, an
unconnected db_server is terminated by its host’s albd_server.
db_server
db_server进程管理VOB数据库事务在那个响应客户端程序发送请求的主机上。因为客户程序不能直接访问VOB数据库，他们必须发送数据库事务请求给db_server进程当他们需要去创建，读取，或者修改VOB数据或者元数据。
每个db_server进程服务在同一时间只服务单个客户端，但是可以操作任何数量的VOBs。客户端创建一个连接到db_server通过在VOB主机上的albd_server进程的帮助，如果有必要，albd_server启动一个新的db_server进程去操作请求。当客户端退出或者空闲（停止请求数据库事务由于延迟时间）的时候，连接将会被断开。在那种情况，db_server变得可用的被其他的客户端，当空闲一段时期后一个未连接的db_server将被那个主机的albd_server关闭。
vobrpc_server
Each VOB server host runs one or more vobrpc_server processes for each of its VOBs.
Each vobrpc_server process handles requests from view_server processes throughout
the network. These requests can generate both metadata (VOB database) and file
system data (storage pool) activity. The vobrpc_server accesses the VOB database in
the same way as a db_server; it forwards storage pool access requests to the
vob_server.
12 Administrator’s Guide: Rational ClearCase and Rational ClearCase LT
vobrpc_server processes are started by albd_server, which also routes new requests to
the least-busy servers and terminates unneeded vobrpc_server processes when the
system is lightly loaded.
vobrpc_server
每个VOB服务主机运行一个或更多的vobrpc_server进程对每个VOBS。每个vobrpc_server进程操作来自网络的view_server进程的请求。这些请求能生成元数据（VOB数据库）和文件系统数据（存储池）活动。Vobrpc_server访问VOB数据库德方式和db_server访问方式一样，它的前向的存储池访问请求给vob_server.
Vobrpc_server进程通过albd_server启动，它发送新的请求给最闲的服务并且关闭不需要的vobrpc_server进程当系统不是很繁忙的时候
lockmgr
Each VOB server host runs one lock manager process, lockmgr, which arbitrates
transaction requests to all VOB databases on that host. The calling program polls
lockmgr, which either grants or prohibits access to the requested data. If the data is
available, the transaction proceeds immediately: the data is read or written, and output
is returned to the calling program. If the data is unavailable (locked because another
caller has been granted write access to the data), the caller waits until lockmgr grants
it access to the data.
Unlike most other ClearCase services, the lockmgr is not started by the albd_server.
Instead, it is started when the VOB host starts. Lock manager startup options can be
changed if necessary to improve VOB server performance for certain configurations.
For more information, see Modify Lock Manager Startup Options on page 291.
Lockmgr
每个VOB服务器运行了一个锁定管理进程，lockmgr，它平等的处理所有在服务器上的VOB数据库的请求。Lockmgr，调用的程序池，不是同意就是拒绝数据的访问请求。如果数据可用，立即进行处理。数据或读，或写，并且输出返回到了调用程序。如果数据不可用（由于其他的调用者已经同意对数据的写访问而被锁定），调用者就得等待知道lockmgr同意他对数据的访问。
不想ClearCase其他大多数服务，lockmgr不被albd_server启动，相反，当VOB主机启动的时候他就启动了。锁定管理启动选项可以被改变如果有必要通过一定的配置去改进VOB服务器性能。