Temporal server states and RD_TIMEOUT parameters

Changes of the server states (SS, HS, SBS, CS) are also characterized by changing its states into temporal states, which are specified by RD parameters given in seconds. The list of temporal states is shown in the following table:

The basic assumption for the correct setting is to know the time (T_START), that is required for starting the server on particular platform. The server start time is the time from starting the server to the moment when the server is able to connect to a client. It depends mainly on the configuration database size, which is read by the server. You must realize, that the time increases along with extending the application.

iNone

Stable state. The server in this state has already read the configuration database. If the server is SBS, the configuration database is synchronized with the HS configuration database. Next configuration changes are replied in real time.

iElection

The state, when a HS is not selected. This state is the time, when the servers, which are able to change their states into the HS state, swap own RDS parameters (using MULTICAST) in order to choose a new HS. The state is terminated by:

1. expiration of the specified time. The server then set itself as HS. The server notifies the other RDG servers about it.
2. detection of a RDG member with a higher priority. The server then is waiting for the HS registration.
3. detection that a HS is in the RDG.

Recommended period of this state is 5 to 10 seconds (10 seconds for OpenVMS platforms).
RD_TIMEOUT_iElection = 7

iWaitingHot

The time period, when the server is waits for the HS registration. Server is in this state when:

1. there is no HS but there is an information that some of the RDG members will become the HS because of its priority.
2. there is no HS and the server cannot change its status into the HS state, because its priority is 0. The state will be terminated if a HS is registered or operator sets a HS server manually.

Recommended minimum period of the state is
RD_TIMEOUT_iWaitingHot = RD_TIMEOUT_iElection * 1.25.
It is 25 % longer than the iElection state.

iWaitingReadyHot

The time when the server waits for the ready HS. Server is in this state, when it is known which server is to be the HS, but the HS is not completely ready for its functioning (cannot connect a client), because is reading the configuration database. The time period of the state is at least the time T_START. The state is terminated, when the HS notify the other server that it is completely ready. If the server is in the state after unexpected failure of the HS, the server automatically changes its status to the CS status (it will be restarted).

Recommended minimum period is T_START*1.5.

RD_TIMEOUT_iWaitingHot = T_START*1.5

iStartingKernelToSBS

The time when the server:

1. is establishing the connection to the HS
2. is requiring the database synchronization from the HS and the synchronization will be successfully finished
3. is reading the configuration database

The configuration database synchronization time strongly depends on the size of the databases and the differences between them. If the server is stopped for a short time, the configuration are almost identical or minimal and the synchronization time is reduced to reading the databases.

Required minimum period of the state is T_START*2.5.

RD_TIMEOUT_iStartingKernelToSBS = T_START * 2.5

iStartingKernelToHOT

The server is in the state after:

1. starting if it was chosen to be the HS
2. manual switching the server with the priority of 0 to the HS state if there is not another HS

The server reads the configuration database in the state. The time period of the state is at least T_START.

Recommended minimum period of the state is T_START*1.5.

RD_TIMEOUT_iStartingKernelToHot = T_START * 1.5

iHotOrSBSToSBS_WaitForHot

Operator switches one server manually to the HS state. All servers, except the switched server, are to be in the state. The state is the time when the expectant SBS servers are waiting for confirmation of the HS state. Practically, the change takes a short time and the period should be set to the value equal to RD_TIMEOUT_iWaitingHot.

iHotOrSBSToSBS_WaitAnsConn

If a server is still in the SBS state and is waiting for confirmation or establishing the connection to the HS after manual switching the HS, then we can say the server is in the state iHotOrSBSToSBS_WaitAnsConn. Practically, the change takes a short time and the period should be set to the value equal to RD_TIMEOUT_iWaitingHot.