Following two server processes 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.
albd_server
admin_server
Following other server processes are started as necessary tomanage any VOBs and views that reside on the host:
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
· Responding to requests for registry information (on ClearCase registry server host)
· Responding to requests for licenses (on ClearCase license server host)
· Responding to load-balancing queries from a remote clearmake process (on UNIX hosts)
Notes:
1. albd_server process starts first when ClearCase is started on a host.
2. albd_server doen't get installed on a host without support for local VOBs and views.
3. albd_server listens for RPCs on a well-known port (port 371) that has been reserved for it by the Internet Assigned Numbers Authority.
admin_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 (backup registry server host)
credmap_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 hosts.
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.
vob_server:
vob_server process runs on the VOB host one for each VOB as needed by albd_server. The vob_server manipulates data in the VOB’s storage pools in response to requests from client processes. A vob_server process is started . 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
db_server:
db_server processes manage VOB database transactions on that host in response to requests from client programs. 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. db_server becomes available for use by another client once current connection terminates. After a period of idleness, an unconnected db_server is terminated by its host’s albd_server.
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. 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.
lockmgr:
Each VOB server host runs one lockmgr process 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. Unlike most other ClearCase services, the lockmgr is not started by the albd_server but started when the VOB host starts.
rwp:
rwp provides application support for the ClearCase Web interface. RWP servers are normally configured at install time and need no further administrative attention unless special configurations. A ClearCase community may have one or more rwp servers.
How ClearCase Client communicates with ClearCase Server?
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.