The current maxima for the size of a journal are:

Number of blocks per disk: 524288
(This is max_segments_per_disk * disk_blocks_per_segment , or 16384 times 32.)
Number of disks per journal: 16.

Shadowed sites can either be two nodes within a single cluster, or can be two separate clusters. In the second case you can also configure standby servers on one or more of the other cluster members, so that failure of a single node within one of the shadow sites does not stop the shadow site from functioning. Multiple concurrent copies of the server processes are allowed on each site (see Figure 5-1).

Figure 5-1 Four Node Shadow/Standby Configuration

The performance of a shadow pair compares with a transaction that spans two nodes, with the addition of one extra protocol message which is required to ensure that the transactions are presented in the same order.

RTR does not have to wait for the secondary shadow server to complete its processing. It only needs to know that the primary has committed the transaction and that the journal file of the secondary shadow server contains the final vote status.

The two partners in a shadow pair should be connected with sufficient bandwidth to allow for the large amounts of data which may need to be transferred during a shadow catchup operation.

5.7 Shadows in Action

The first node on which a shadow backend for a particular key range starts is arbitrarily designated by RTR to be the primary site for that key range.

Initially RTR searches the journals of other backend nodes to find any recoverable transactions left over from a previous invocation of the backend. Once these have been processed (or RTR determines that no such transactions exist), the backend becomes active and available to handle new transactions sent by clients/frontends.

While no other backend node for this key range is available, the backend runs in REMEMBER mode. RTR saves transactions processed on this site in the RTR journal (together with the order in which they should be committed), so that when the other-site backends start, they can be sent to this site.

When a backend starts on a second site, it begins processing the transactions saved in the primary site's journal. These are deleted from the journal as they are processed. When the second site backends have caught up, the second backend enters SECONDARY ACTIVE state and the original site backends enter PRIMARY ACTIVE state. In this mode, new transactions are sent to both sites in parallel. They are executed first on the primary site, and shortly afterward on the secondary site in the same order. The primary site commits transactions as soon as it knows that the secondary site has hardened (i.e., written to the journal) the order in which the transaction is to be committed.

If a failure occurs at this point, the remaining site executes a short cleanup operation. After completing the cleanup operation and determining that the other site is really down, it reverts to the REMEMBER state and continues processing new transactions autonomously, saving the transaction information in its journal for when the other site restarts.

The execution order is determined for transactions issued to concurrent servers on a particular node by recording the order in which the individual servers issue rtr_accept_tx() calls. RTR knows that at the time a correctly written server application calls rtr_accept_tx() , it has already accessed (and therefore locked) any database records it uses, and that it will release these records after RTR causes the rtr_accept_tx() call to complete. Any conflicting transaction would not be able to issue rtr_accept_tx() concurrently. Therefore a correct serialization order for issuing the transactions on the shadow site can be determined.

5.8 Application Considerations

Although applications need not be directly concerned about shadowing matters, certain points must be considered when implementing performance boosting optimizations:

• Anything specific to the executing node should not be stored in the database, since this would lead to diverging copies.
• Any physical reference to the transaction which is unique to the executing server, e.g. Channel ID, system time, DB-key, etc., should not be passed back to the client for future references within its subsequent messages. This could lead to inconsistent handling when a different server is involved in shadow operations.
  This consideration is also valid for recovery of non-shadowed servers.

For more information on designing applications, see the Design for Tolerating Site Disaster section in the RTR Application Design Guide.

5.9 Server States

The current state of a server can be examined as follows:

RTR> show server/full Servers: Process-id: 13340 Facility: RTR$DEFAULT_FACILITY Channel: 131073 Flags: SRV State: active Low Bound: High Bound: 87 13 rcpnam: "RTR$DEFAULT_CHANNEL" User Events: 0 RTR Events: 0 Partition-Id: 16777216 Process-id: 13340 Facility: RTR$DEFAULT_FACILITY Channel: 196610 Flags: SRV State: active Low Bound: 88 13 High Bound: 0f' rcpnam: "CHAN2" User Events: 0 RTR Events: 0 Partition-Id: 16777217

Figure 5-2 gives an overview of the server state changes which appear in the State: field.

Figure 5-2 Backend Server States

5.10 Client States

RTR> show client/full Clients: Process-id: 13340 Facility: RTR$DEFAULT_FACILITY Channel: 458755 Flags: CLI State: declared rcpnam: "CHAN3" User Events: 255 RTR Events: 0

Figure 5-3 describes the client state changes which appear in the State: field.

Figure 5-3 Frontend Client States

5.11 Partition States

RTR> show partition/router/full Facility: RTR$DEFAULT_FACILITY State: ACTIVE Low Bound: 0 High Bound: 4294967295 Failover policy: fail_to_standby Backends: node10 States: active Primary Main: node10 Shadow Main:

Backend partitions:

RTR> show partition/backend/full Partition name: RTR$DEFAULT_PARTITION_16777217 Facility: RTR$DEFAULT_FACILITY State: active Low Bound: "aaaa" High Bound: "mmmm" Active Servers: 0 Free Servers: 1 Transaction presentation: active Last Rcvy BE: Txns Active: 0 Txns Rcvrd: 0 Failover policy: fail_to_standby Key range ID: 16777217 Partition name: RTR$DEFAULT_PARTITION_16777218 Facility: RTR$DEFAULT_FACILITY State: active Low Bound: "nnnn" High Bound: "zzzz" Active Servers: 0 Free Servers: 1 Transaction presentation: active Last Rcvy BE: Txns Active: 0 Txns Rcvrd: 0 Failover policy: fail_to_standby Key range ID: 16777218

Figure 5-4 describes the partition state changes which appear in the State: field.

Figure 5-4 Router Partition States

This chapter contains a description of the RTR monitor. The RTR monitor allows you to view the activities of RTR and your applications. Many different aspects of RTR's behavior can be viewed, allowing the activities and performance of RTR to be analyzed.

6.1 Introduction

It can be used to check the correct operation of an RTR network, showing information useful for tuning, capacity planning, and locating configuration and application errors.

The information displayed is composed of named data items which are continuously updated by RTR. These data items can be displayed in various formats and combined using simple arithmetic operators and constants.

The monitor is invoked with the MONITOR command. MONITOR displays a monitor picture that is periodically updated. See Section 7.2 for the full syntax of the MONITOR command.

A monitor picture contains elements that are either text (such as labels and titles) or variables derived from data items. Monitor pictures can be defined either interactively at the RTR> prompt or defined in a file called a monitor file.

You can use monitor files provided with RTR and you can create your own. See Appendix A for information about creating monitor files.

6.2 Standard Monitor Pictures

A number of standard monitor pictures are supplied with RTR. These cover most of the usual monitoring requirements. You may define your own monitor pictures or alter the standard ones to suit your particular needs. Table 6-1 contains a list of the standard monitor pictures. To display one of these pictures, use the following command at the RTR prompt:

RTR> MONITOR picture-name

The files for standard monitor pictures are installed on your system when RTR is installed. The location of these files is platform specific. The file names are the picture name appended with .mon . Type the file name without .mon when starting the display.

See Chapter 7, RTR Commands, for more information on the MONITOR command.

Table 6-1 Standard Monitor Pictures

Picture name	Description
accfail	Shows link transport name for links on which a connection attempt was declined, with a reason for failure. The most recent entry is highlighted.
acp2app	Displays counts of messages and number of bytes from RTRACP to the application, as viewed from a specific node.
active	Displays a list of RTR processes, and for each process the number of transactions they have started, the number of transactions they have completed and the number of transactions that are still active.
app2acp	Displays counts of messages and number of bytes from the application to RTRACP, as viewed from a specific node.
appdelay	Displays counts of flow-control induced traffic stalls by application process.
broadcast	Displays information about RTR user events by process, including number of user events enqueued, received, and discarded.
calls	Displays the total number of RTR API calls and their success or failure for the processes on all the nodes being monitored. All RTR messages are also shown by message type. (Pending messages are those that an application has not received yet). Use the /IDENTIFICATION=process-id qualifier to display the values for one specific process, otherwise the total values for all processes are displayed.
channel	Displays the roles of the channels declared by an application. This can be useful as a debugging tool in the early stages of application development.
connects	Displays connection status summary, including the number of links up and down, and a list of links with state (up or down), architecture, network transport, and fail-reason, if any.
ctccalls	Displays the history of calls for a specific client transaction controller.
downstream	Displays counts of downstream flow-control induced traffic stalls.
event	Displays event routing data by facility. Information includes events in transit and destination information showing number of events enqueued, processed, and discarded.
flow	Displays the flow control counters.
flostalls	Displays counts of flow-control induced traffic stalls.
frontend	Displays frontend status and counts by node and facility, including frontend state current router, reject status, retry count, and quorum rejects.
group	Shows server and transaction concurrency on a partition basis.
ipc	Shows counts of interprocess communication (IPC) activity in the RTR ACP and active RTR applications.
ipcrate	Displays rate information on IPC messages, byte counts, and I/O primitive usage.
journal	Displays the current journal usage on a node. Local node journal statistics are provided, and data for non local journals accessed from the local node. Includes statistics covering total number of entries and records written, the number of records read, and how many bytes were involved. Bar graphs showing current usage of journal blocks (as a percentage of the total) are also provided.
link	Displays a number of per-link data items. Use the /LINK=link-name qualifier to display the values for one specific link, otherwise the total values for all links are displayed.
netbytes	Displays a list of the links to other nodes. For each link, the total number of bytes received and sent on that link and the number of bytes received and sent per second are displayed.
netstat	Displays for each link the connection status in detail, with the link state (up or down), and architecture type of remote node (such as VAX, I386, Alpha, and so on).
ortr	Displays a list of server/client transaction controllers.
partit	Displays the status of server partitions. Shows the partition identifiers, key ranges and key segments, and the status of the servers (active, recovering and so on).
queues	Shows transaction queues on a partition basis.
quorum	Tracks (by facility) the configuration, reachability, and quorum status of one or more nodes.
recovery	Displays the status of server recovery procedures, such as waiting for quorum, catching up transactions, and so on.
rejects	Displays the last rtr_mt_rejected message received by each running process.
rejhist	Displays the last 10 rtr_mt_rejected messages received by the selected process.
response	Displays the elapsed time that a transaction has been active on the opened channels of a process.
rolequor	Displays a detailed picture of the various data items in the QUORUM picture, separated by roles. If a quorum problem is encountered, this picture may be useful for problem diagnosis.
routers	Displays information on a router node. It gives an indication of the utilization of the router in terms of transactions and broadcasts routed through this node. Useful to monitor performance or locate problems.
routing	Displays statistics of transaction and broadcast traffic by facility.
rscbe	Displays the most recent call's history for the RSC subsystem on a backend node.
stalls	Displays in real time any network links currently stalling in their outbound traffic, and provides a history of the stalls that the various links encountered during their lifetime.
stccalls	Displays a history of calls for a specified server transaction controller.
system	Displays the state of critical resources within the RTR environment. If a resource has exceeded a predefined threshold, a warning indicator is displayed.
tps	Displays the rate of transaction commits performed by each process using RTR.
tpslo	Displays low end of the rate of transaction commits performed by each process using RTR.
traffic	Displays a list of the links to other nodes. Shown for each link are: byte rate, packet rate, message rate and congestion, in both directions. Average packets per second is also shown.
trans	Displays transactions for a frontend, router and backend.
upstream	Displays upstream flow-control induced traffic stalls.
v2calls	Shows RTR Version 2 verb usage through the interoperability subsystem. The screen layout is identical to the RTR Version 2 Monitor Call's picture.
xa	Displays XA counter information including success and failure as well as call and read-only counters.

The following sections describe the more commonly used standard monitor pictures in detail.

6.2.1 Monitor Accfail (Link Acceptance Failures)

When configuring RTR, nodes can sometimes fail to connect up. Although the cause of the error can be viewed on the initiator side with the MONITOR NETSTAT picture, it can be difficult to pinpoint the problem when looking at the other end of the link. Use the MONITOR ACCFAIL picture to display the reason for the local node's refusal to accept connections.

================================================================================ U n a c c e p t a b l e L i n k s Most recent links on which a connection attempt was declined Node: NODE11 Wed Jan 7 1998 10:51:00 -------------------------------------------------------------------------------- Link Transport Name(s) Reason for failure -------------------------------------------------------------------------------- nodef node is not configured for the facility marke.zko.dec.com node not recognized real1 facility name not matched MARKE DEC:.ZKO.MARKE node not recognized nodef node is not configured for the facility marke.zko.dec.com node not recognized real1 facility name not matched nodez node role definitions do not match for real1 facility name not matched MARKE DEC:.ZKO.MARKE node not recognized -------------------------------------------------------------------------------- List entries are reused in a cyclical fashion; the most recent entry is highlighted. ================================================================================

Some errors that can be displayed by ACCFAIL include:

• RTR_STS_NOTRECOGNISED - "node not recognized"
  The local node has received a connection request over a link that is not configured in any facility on the local machine. If you expected the connection to succeed as the result of having a template link defined, check carefully the names displayed in the monitor picture. These are the names obtained from the network transport over which the link connection attempt was received, and it is with these that a match with a template (wildcard specification) link must succeed. Remember that the name match is performed in a case-sensitive manner. Names corresponding to TCP links may or may nor contain your domain name, depending on how the name is entered in either your local hosts file or name server. DECnet-Plus systems may yield both a pseudonym and a link name; both are checked for a match with a template.
• RTR_STS_FACNOTDEC - "facility name not matched"
  The connecting link is configured, but the facility that it requests does not exist on the local node.
• RTR_STS_NODENOTCNFG - "node is not configured for the facility"
  The connecting link is configured on the local node, but not as part of the requested facility.
• RTR_STS_ROLESMISMATCH - "node role definitions do not match for this facility"
  The connecting link is configured in the requested facility, but with a different role configuration on the local node.
• RTR_STS_TRNOQUO - "router has no quorum in facility %s"
  The router is unable to accept frontend connections since it is not quorate. This condition will clear up automatically as soon as the router gains connections to sufficient backends.