Document revision date: 30 March 2001 | |
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This section contains the following information to help you plan for using DECdtm in a DECnet-Plus network:
DECdtm does not support multiple DECnet-Plus namespaces.
This means that if you want to use software that uses DECdtm services,
you cannot use both a local namespace and a DECdns namespace.
27.3.2 Planning SCSNODE Names in Your DECnet-Plus Network
SCSNODE is a system parameter that defines the name of the computer. You must follow certain rules when choosing SCSNODE names if you have a DECnet-Plus network and you want to perform DECdtm transactions that span either different OpenVMS Clusters or different standalone computers.
27.3.2.1 Rules for SCSNODE Names
If you have a DECnet-Plus network and want to perform DECdtm
transactions that span different OpenVMS Clusters or different
standalone computers, you must make sure that your SCSNODE names obey
the following rules:
A transaction group is a group of computers involved in DECdtm transactions whose SCSNODE names must obey the rules described in Section 27.3.2.1.
A transaction group conforms to the following guidelines:
Figure 27-2 shows an example of a transaction group.
Figure 27-2 Transaction Group
All nine computers shown in the figure are in the same transaction group because:
Before a node can perform DECdtm transactions, you must create a transaction log for the node. In an OpenVMS Cluster environment, create a transaction log for each node.
Removing a node from a cluster after you have created the transaction logs can lead to data corruption. For instructions on how to remove a node safely, see Section 27.11. |
DEFINE/SYSTEM/EXECUTIVE_MODE SYS$JOURNAL dirspec[,...] |
where dirspec is the full specification of a directory in
which you want to create one or more transaction logs. List all the
directories that will contain transaction logs. You can list the
directories in any order.
In a cluster environment, use SYSMAN to
define SYS$JOURNAL clusterwide.
CREATE LOG [/SIZE=size] dirspecSYSTEM$node.LM$JOURNAL |
where:
size | is the size of the transaction log in blocks. By default, the size of the transaction log is 4000 blocks. |
dirspec | is the full specification of the directory in which you want to create the transaction log. |
node | is the name of the node. |
Step | Action | ||||
---|---|---|---|---|---|
a. |
Check whether the logical SYS$DECDTM_INHIBIT is defined:
$ SHOW LOGICAL SYS$DECDTM_INHIBIT |
||||
b. |
Is SYS$DECDTM_INHIBIT defined?
|
This example shows how to create transaction logs in an OpenVMS Cluster that consists of two nodes whose SCSNODE names are BLUE and RED. Neither node has a node-specific version of SYLOGICALS.COM.
Decide the size and location of the transaction logs:
Node | Size of Log (in Blocks) | Disk |
---|---|---|
BLUE | 5000 | DUA1 |
RED | 4000 | DUA2 |
Mount the disks clusterwide:
$ MOUNT/CLUSTER/SYSTEM DUA1: LOG1 $ MOUNT/CLUSTER/SYSTEM DUA2: LOG2 |
Create directories for the transaction logs:
$ CREATE/DIRECTORY DISK$LOG1:[LOGFILES] $ CREATE/DIRECTORY DISK$LOG2:[LOGFILES] |
Define SYS$JOURNAL:
$ RUN SYS$SYSTEM:SYSMAN SYSMAN> SET ENVIRONMENT/CLUSTER SYSMAN> DO DEFINE/SYSTEM/EXECUTIVE_MODE SYS$JOURNAL - _SYSMAN> DISK$LOG1:[LOGFILES], DISK$LOG2:[LOGFILES] SYSMAN> EXIT |
Edit the SYS$MANAGER:SYLOGICALS.COM command procedure to include the following line:
$ ! $ DEFINE/SYSTEM/EXECUTIVE_MODE SYS$JOURNAL DISK$LOG1:[LOGFILES], - DISK$LOG2:[LOGFILES] $ ! |
Create the transaction logs:
$ RUN SYS$SYSTEM:LMCP LMCP> CREATE LOG/SIZE=5000 DISK$LOG1:[LOGFILES]SYSTEM$BLUE.LM$JOURNAL LMCP> CREATE LOG DISK$LOG2:[LOGFILES]SYSTEM$RED.LM$JOURNAL LMCP> EXIT |
Make sure DECdtm services are enabled:
$ SHOW LOGICAL SYS$DECDTM_INHIBIT %SHOW-S-NOTRAN, no translation for logical name SYS$DECDTM_INHIBIT |
SYS$DECDTM_INHIBIT is undefined, so DECdtm services are enabled.
27.5 Monitoring Transaction Performance
Changes to your system, such as increase in work load, can affect transaction performance. Once a month, monitor transactions on the node to make sure that transaction performance has not deteriorated. In an OpenVMS Cluster environment, monitor transaction performance on all the nodes in the cluster.
MONITOR TRANSACTION/SUMMARY[=file-spec]/ENDING=time/NODE=(nodename,...) |
where:
file-spec | is the file specification of the summary file. Information about transactions is summarized and recorded in the summary file. If you omit the file specification, the information is recorded in MONITOR.SUM in your default directory. |
time | is the time that the monitoring session ends. |
nodename | is the name of a node. In an OpenVMS Cluster, list all the nodes in the cluster. |
Less than 1 second
Between 1 and 2 seconds
Between 2 and 3 seconds
Between 3 and 4 seconds
Between 4 and 5 seconds
More than 5 seconds
This example shows how to monitor transaction performance on an OpenVMS Cluster that consists of two nodes whose SCSNODE names are BLUE and RED.
Monitor transactions on nodes BLUE and RED for one day:
$ MONITOR TRANSACTION/SUMMARY=DISK$LOG1:[LOGFILES]TRANSACTIONS.SUM - _$ /ENDING="+1-"/NODE=(BLUE,RED) |
Examine the summary file:
DISTRIBUTED TRANSACTION STATISTICS on node BLUE From: 16-OCT-2000 14:23:51 SUMMARY To: 17-OCT-2000 14:23:51 CUR AVE MIN MAX Start Rate 49.02 43.21 31.30 49.02 Prepare Rate 48.70 43.23 30.67 48.70 One Phase Commit Rate 0.00 0.00 0.00 0.00 Total Commit Rate 48.70 43.19 31.30 48.70 Abort Rate 0.00 0.00 0.00 0.00 End Rate 48.70 43.19 31.30 48.70 Remote Start Rate 0.00 0.00 0.00 0.00 Remote Add Rate 0.00 0.00 0.00 0.00 Completion Rate 0-1 21.42 13.57 0.63 21.42 by Duration 1-2 25.97 29.15 24.59 33.87 in Seconds 2-3 1.29 0.47 0.00 4.47 3-4 0.00 0.00 0.00 0.00 4-5 0.00 0.00 0.00 0.00 5+ 0.00 0.00 0.00 0.00 SUMMARIZING DISTRIBUTED TRANSACTION STATISTICS on node RED From: 16-OCT-2000 14:23:52 SUMMARY To: 17-OCT-2000 14:23:52 . . . |
Make a note of the following values:
13.57 transactions completed in 0 to 1 seconds
29.15 transactions completed in 1 to 2 seconds
0.47 transactions completed in 2 to 3 seconds
Compare the results from this monitoring session to those of previous sessions:
Session | End Rate | Completion Rates | ||
---|---|---|---|---|
0--1 Secs | 1--2 Secs | 2--3 Secs | ||
June | 42.13 | 12.98 | 28.13 | 1.02 |
July | 38.16 | 10.35 | 25.80 | 2.01 |
August | 43.19 | 13.57 | 29.15 | 0.47 |
The results for node BLUE show no signs of deteriorating performance.
27.6 Checking Whether a Transaction Log Is Too Small
If transaction performance has deteriorated on a node, check whether its transaction log is too small.
Section 27.5 describes how to find out whether transaction performance has deteriorated.
$ RUN SYS$SYSTEM:LMCP LMCP> SHOW LOG/CURRENT |
This example shows how to check whether node BLUE's transaction log is too small.
Log in to node BLUE. Then check how many times the transaction log has stalled:
$ RUN SYS$SYSTEM:LMCP LMCP> SHOW LOG/CURRENT Checkpoint starts/ends 2464/2464 Stall starts/ends 21/21 Log status: no checkpoint in progress, no stall in progress. |
The number of checkpoints is 2464, and the transaction log has stalled 21 times.
Wait for five minutes, then repeat the SHOW LOG/CURRENT command:
LMCP> SHOW LOG/CURRENT Checkpoint starts/ends 2514/2514 Stall starts/ends 28/28 Log status: no checkpoint in progress, no stall in progress. |
The number of checkpoints has increased since the previous reading, and
the transaction log has now stalled 28 times, an increase of 7. This
means that the transaction log is too small.
27.7 Changing the Size of a Transaction Log
To determine if changing the size of a transaction log is necessary, see Section 27.6.
Follow all the steps carefully. Taking shortcuts can lead to data corruption. |
SHOW LOG SYSTEM$node.LM$JOURNAL |
where node is the name of the node that the transaction
log belongs to.
RENAME dirspecSYSTEM$node.LM$JOURNAL dirspecSYSTEM$node.LM$OLD |
where:
dirspec | is the full specification of the directory containing the transaction log. |
node | is the name of the node that the transaction log belongs to. |
Yes |
Close the transaction log as follows:
|
||||||||||||
No | Close the transaction log by rebooting the node. Log in to the node when it has rebooted. |
CONVERT LOG/SIZE=size dirspecSYSTEM$node.LM$OLD dirspecSYSTEM$node.LM$JOURNAL |
where:
size | is the new size of the transaction log in blocks. |
dirspec | is the full specification of the directory containing the transaction log. |
node | is the name of the node that the transaction log belongs to. |
DELETE dirspecSYSTEM$node.LM$OLD; |
where:
dirspec | is the full specification of the directory containing the old transaction log. |
node | is the name of the node that the transaction log belongs to. |
This example shows how to change the size of node RED's transaction log to 6000 blocks. Node RED is in an OpenVMS Cluster, and its transaction log is in DISK$LOG2:[LOGFILES].
Log in to node RED. Find out which directory RED's transaction log is in, then rename the transaction log:
$ RUN SYS$SYSTEM:LMCP LMCP> SHOW LOG SYSTEM$RED.LM$JOURNAL Directory of DISK$LOG2:[LOGFILES] SYSTEM$RED.LM$JOURNAL;1 Total of 1 file. LMCP> EXIT $ RENAME DISK$LOG2:[LOGFILES]SYSTEM$RED.LM$JOURNAL - _$ DISK$LOG2:[LOGFILES]SYSTEM$RED.LM$OLD |
Stop all software that uses DECdtm services. Then close the transaction log:
$ RUN SYS$SYSTEM:LMCP LMCP> CLOSE LOG Transaction log closed, TP_SERVER process stopped LMCP> EXIT |
Restart the TP_SERVER process:
$ @ SYS$STARTUP:DECDTM$STARTUP.COM |
Change the size of the transaction log:
$ RUN SYS$SYSTEM:LMCP LMCP> CONVERT LOG/SIZE=6000 DISK$LOG2:[LOGFILES]SYSTEM$RED.LM$OLD - _LMCP> DISK$LOG2:[LOGFILES]SYSTEM$RED.LM$JOURNAL Log file DISK$LOG2:[LOGFILES]SYSTEM$RED.LM$JOURNAL;1 created. Log file DISK$LOG2:[LOGFILES]SYSTEM$RED.LM$OLD converted. LMCP> EXIT |
Restart the software that uses DECdtm services.
Delete the old transaction log:
$ DELETE DISK$LOG2:[LOGFILES]SYSTEM$RED.LM$OLD; |
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