| Oracle® Database Oracle Clusterware and Oracle Real Application Clusters Administration and Deployment Guide 10g Release 2 (10.2) Part Number B14197-03 |
|
|
View PDF |
| Oracle® Database Oracle Clusterware and Oracle Real Application Clusters Administration and Deployment Guide 10g Release 2 (10.2) Part Number B14197-03 |
|
|
View PDF |
This chapter explains how you can extend the high availability of the Oracle Clusterware framework to your applications. You do this by wrapping your applications with Oracle Clusterware commands. That is, you can use the same high availability mechanisms of the Oracle database and Real Application Clusters to make your custom applications highly available. You can use Oracle Clusterware to monitor, relocate, and restart your applications as described in this chapter under the following topics:
Overview of Managing Custom Applications with Oracle Clusterware Commands
Example of Using Oracle Clusterware Commands to Create Application Resources
Using Oracle Clusterware Commands
See Also:
Appendix B, "High Availability Oracle Clusterware Command-Line Reference and C API" for detailed information about Oracle Clusterware commands and Appendix C, "Oracle Clusterware Messages" for information about Oracle Clusterware error messagesNote:
You can install the Oracle Clusterware high availability Application Programming Interface (API) from the Oracle Database 10g release 10.2 client installation media. As described in this chapter, you can use the API to integrate non-oracle applications with Oracle Clusterware to make them highly available.The Oracle Clusterware includes a high availability framework that provides an infrastructure to manage any application. The Oracle Clusterware ensures that applications that it manages start when the system starts. The Oracle Clusterware also monitors the applications to make sure that they are always available. For example, if a process fails, then Oracle Clusterware attempts to restart the process based on scripts that you customize. If a node in the cluster fails, then you can program processes that normally run on the failed node to restart on another node. The monitoring frequency, starting, and stopping of the applications and the application dependencies are configurable.
To make applications highly available, first create an application profile that identifies your application. The application profile uses a second component, an action program, that describes how Oracle Clusterware should monitor your application and how Oracle Clusterware should respond to changes in your application's status. Oracle stores application profile attributes in the OCR. The definitions of an application profile, action program, and the other primary Oracle Clusterware high availability components are as follows:
Action Program—A program that defines the location of your program, the monitoring frequency, and the start and stop actions that Oracle Clusterware should perform on the application. The start action starts the application, the stop action stops the application, and the monitoring or check action checks the application's status.
Application Profile—An Oracle Clusterware resource file that describes the attributes of your application. An application profile influences your application's behavior and it identifies other programs or scripts that Oracle Clusterware should run to perform various actions.
Privileges—Access and usage privileges that enable Oracle Clusterware to control all of the components of your application for high availability operations, including the right to start processes under other user identities. The Oracle Clusterware must run as a privileged user to control applications with the correct start and stop processes. On UNIX-based platforms, this usually implies that Oracle Clusterware must run as the root user and on Windows-based platforms Oracle Clusterware must run as Administrator.
Resource—An entity that Oracle Clusterware manages for high availability such as your application.
Note:
A resource in the Oracle Clusterware context is not the same as a resource in the Oracle database sense, such as "Resource Manager". A resource that Oracle Clusterware uses only refers to application programs.Resource Dependency—A relationship among resources or applications that implies an operational ordering. For example, during a start operation, parent resources are started before resources that have dependencies. During a stop, the most dependent resources are stopped first.
Oracle Cluster Registry (OCR)—A mechanism that stores configuration information that Oracle Clusterware and other RAC manageability systems use. The OCR uses a hierarchical name space for key value pairs. Keys and subkeys have enforced user, group, and other permissions. The OCR is stored either on a shared raw partition or on a non-cached, shared file system file.
Template—A user-created text file that contains the default values for application profile attributes. Template files contain default values for profile attributes.
See Also:
Appendix B, "High Availability Oracle Clusterware Command-Line Reference and C API" for more information about using Oracle Clusterware commands to make your applications highly availableYou can use the Oracle Clusterware commands to start, stop, relocate, and check the status of your custom applications. Do this by defining your application with an application profile. The profile defines attributes that affect how Oracle Clusterware manages your application. Then register your application information in the OCR using the crs_register command. Use the following steps to create an application profile:
Create an application profile by editing an ASCII file or by running the crs_profile command. Refer to Table 14-1 for a listing of required and optional entries for the Oracle Clusterware profiles.
Register the application profile using the crs_register command.
Run the crs_start command to initiate the application profile and then Oracle Clusterware runs the action program command that you have included in the profile to start your application.
The Oracle Clusterware periodically runs the action program command to check an application's status.
In the event of a check or node failure, Oracle Clusterware recovers the applications either by restarting it on the current node or by relocating the application to another node.
If you run the crs_stop command to stop the application, then Oracle Clusterware runs the action program command to stop it.
You can manage application availability as follows:
Specify starting resources during cluster or node start up
Restart applications that fail
Relocate applications to other nodes if they cannot run in their current location
Full administrative privileges are not required when using Oracle Clusterware. Any user can create resources or applications. However, the creator or owner must grant permission to other users or user groups in order for others to be able to use Oracle Clusterware on those applications. Additionally, profiles that have privileges defined can only be modified by privileged users. The following sections provide further details about application profiles.
Note:
Do not use the Oracle Clusterware commands
crs_register, crs_profile, crs_start or crs_stop on resources with names beginning with the prefix ora unless either Oracle Support asks you to, or unless Oracle has certified you as described in http://metalink.oracle.com. Server Control (SRVCTL) is the correct utility to use on Oracle resources. You can create resources that depend on resources that Oracle has defined. You can also use the Oracle Clusterware commands to inspect the configuration and status.Application profiles have attributes that define how Oracle Clusterware starts, manages, and monitors applications. One attribute is the location of the action program that Oracle Clusterware uses to manipulate the application. The Oracle Clusterware uses the action program to monitor or check the application status and to start and stop it. Oracle reads application profiles from files stored in specified locations and stores the information in the OCR. You use the Oracle Clusterware commands within profiles to designate resource dependencies and to determine what happens to an application or service when it loses access to a resource on which it depends.
The filenames of application profiles must be in the form resource_name.cap where resource_name is the name that you or the system assigns to an application and cap is the file suffix. The Oracle Clusterware commands in profiles refer to applications by name, such as resource_name, but not by the full filename. The following section describes this in more detail.
Attributes are defined by name=value entries in profile files and these entries can be in any order in the file. The following are some of the primary attributes of an application profile:
Resources that are required by an application which are defined by settings for the REQUIRED_RESOURCES parameter. The Oracle Clusterware relocates or stops an application if a required resource becomes unavailable. Required resources are defined for each node.
Rules for choosing the node on which to start or restart an application are defined by settings for the PLACEMENT parameter. The application must be accessible by the nodes that you nominate for placement.
A list of nodes to use in order of preference when Oracle Clusterware starts or fails over an application which is defined by settings for the HOSTING_MEMBERS parameter. This list is used if the placement policy defined by the PLACEMENT parameter is favored or restricted.
Application profiles have optional and required profile attributes. Optional profile attributes may be left unspecified in the profile. Optional profile attributes that have default values are merged at registration time with the values that are stored in the template for that resource type and for the generic template. Default values are derived from the template.
Each resource type has a template file named TYPE_resource_type.cap that is stored in the template subdirectory under the crs directory of the Oracle Clusterware home. A generic template file for values that are used in all types of resources is stored in the same location in the file named TYPE_generic.cap.
Table 14-1 lists the Oracle Clusterware application profile attributes in alphabetical order. For each attribute, the table shows whether the attribute is required, its default value, and an attribute description.
Table 14-1 Application Profile Attributes
| Attribute | Required | Default | Description |
|---|---|---|---|
|
|
Yes |
None |
The resource-specific script for starting, stopping, and checking a resource. You may specify a full path for the action program file. Otherwise, the default paths are used: |
|
|
No |
0 |
When set to |
|
|
No |
0 |
A flag indicating whether Oracle Clusterware should automatically start a resource after a cluster restart, regardless of whether the resource was running prior to the cluster restart. When set to |
|
|
No |
60 |
The time interval, in seconds, between repeated executions of the check entry point of a resource's action program. There can be some overhead associated if you set the check interval to a low value and enable frequent checks. |
|
|
No |
Name of the resource |
A description of the resource. |
|
|
No |
0 |
The amount of time, in seconds, that Oracle Clusterware waits before attempting to restart or fail over a resource. |
|
|
No |
0 |
The interval, in seconds, during which Oracle Clusterware applies the failure threshold. If the value is zero ( |
|
|
No |
0 |
The number of failures detected within a specified |
|
|
Sometimes |
None |
An ordered list of cluster nodes separated by blank spaces that can host the resource. This attribute is required only if Enter node names as values for the The node name is usually the same as the physical host name. However, it can be different. For example, when vendor clusterware is present, the Oracle Clusterware nodes are named the same as the vendor clusterware nodes. Not all vendor clusterware implementations use the physical node names as node names. Use the Your |
|
|
Yes |
None |
The name of the application. The application name is a string that contains a combination of letters |
|
|
No |
None |
An ordered list of resource names separated by blank spaces that this resource uses during placement decisions. Up to 58 user-defined resources can be listed. |
|
|
No |
|
The placement policy ( |
|
|
No |
None |
An ordered list of resource names separated by blank spaces that this resource depends on. Each resource to be used as a required resource in this profile must be registered with Oracle Clusterware or the resource's profile registration will fail. |
|
|
No |
1 |
The number of times that Oracle Clusterware attempts to restart a resource on a single cluster node before attempting to relocate the resource. A value of |
|
|
|
|
The counter maintained by the Oracle Clusterware daemon for the number of times that a resource had been restarted. It goes from zero to |
|
|
No |
60 |
The maximum time, in second, that an action program may require to complete before an error is returned. This attribute specifies the time out value for the "check" action of the action script. If the check action does not return before this time, Oracle Clusterware will consider the action failed. |
|
|
|
|
This attribute specifies the timeout value for the "start" action of the action script. If the start action does not return before this time, Oracle Clusterware will consider the action failed. |
|
|
|
|
This attribute specifies the timeout value for the "stop" action of the action script. If the stop action does not return before this time, Oracle Clusterware will consider the action failed. |
|
|
Yes |
None |
Must be |
|
|
|
|
The value for |
Profiles may be located anywhere and need not be on a cluster-visible file system. RAC provides default locations for profiles as described in the next sub-section. The default location for profiles with root privileges on UNIX-based systems or Administrator privileges on Windows-based systems is the profile subdirectory under the crs directory of the Oracle Clusterware home. The default location for profiles with non-root or non-Administrator privileges is the public subdirectory under the crs directory of the Oracle Clusterware home.
The example in this section creates an application named postman. The Oracle Clusterware uses the script /opt/email/bin/crs_postman to start, stop, and monitor whether the application is running (action_script). The Oracle Clusterware checks postman every five seconds as specified by the setting for the check_interval parameter. The Oracle Clusterware restarts postman no more than once if it fails. When deciding on which node to place the postman application, Oracle Clusterware considers the value for the optional_resources parameter. If possible, Oracle Clusterware places postman on the same node. Finally, in order for postman to run, the resource network1 must be running on the same node as specified by the setting for the required_resources parameter. If network1 fails or if it is relocated to another node, then Oracle Clusterware stops or moves the postman application.
Note:
Do not use the Oracle Clusterware commandscrs_register, crs_profile, crs_start or crs_stop on resources with names beginning with the prefix ora unless either Oracle Support asks you to, or unless Oracle has certified you as described in http://metalink.oracle.com. Server Control (SRVCTL) is the correct utility to use on Oracle resources. You can create resources that depend on resources that Oracle has defined. You can also use the Oracle Clusterware commands to inspect the configuration and status.The following example uses the crs_profile command to create an application profile for monitoring email.
# crs_profile -create postman -t application -B /opt/email/bin/crs_postman \ -d "Email Application" -r network1 -l application2 \ -a postman.scr -o ci=5,ft=2,fi=12,ra=2
The contents of the application profile file that the example creates are as follows:
NAME=postman TYPE=application ACTION_SCRIPT=/oracle/crs/script/postman.scr ACTIVE_PLACEMENT=0 AUTO_START=0 CHECK_INTERVAL=5 DESCRIPTION=email app FAILOVER_DELAY=0 FAILURE_INTERVAL=12 FAILURE_THRESHOLD=2 HOSTING_MEMBERS= OPTIONAL_RESOURCES=application2 PLACEMENT=balanced REQUIRED_RESOURCES=network1 RESTART_ATTEMPTS=2 SCRIPT_TIMEOUT=60
See Also:
Appendix B, "High Availability Oracle Clusterware Command-Line Reference and C API" for an explanation of the command optionsThe Oracle Clusterware uses the required resources list, with the placement policy and hosting nodes list, to determine the cluster nodes that are eligible to host an application. Required resources must be ONLINE on the nodes on which the application is running or started.
The failure of a required resource on a hosting node causes Oracle Clusterware to attempt to restart the application on the current node. If RESTART_ATTEMPTS is not set to 0, and if the application cannot start on the current node, then Oracle Clusterware attempts to fail the application over to another node that provides the required resource. Alternatively, Oracle Clusterware stops the application if there is no suitable node. In this case, Oracle Clusterware posts a not restarting event notification.
You can also use required resource lists to start, stop, and relocate groups of interdependent applications when you use the crs_start, crs_stop, or crs_relocate commands with the force (-f) option. In other words, you can configure a set of resources to have other required resources. For example you can configure resources A, B, and C where A and B depend on C. Then if you stop resource C with -force option, this action will stop all three resources. The same is true for the crs_relocate command.
In addition, using the -force option can relocate an online dependency, if necessary, to enable the starting of a resource. For instance, assume that resource VIP_A that has a primary node assignment of node A is running instead on node B. If you perform a crs_start on the instance resource for node A, then this operation will fail. This is because the VIP_A resource is required for the instance on node A and the VIP_A resource is online. However, the resource is on a node where the resource cannot run. Performing a crs_start -f on instance B, however, forces the VIP_A resource to relocate and then start the instance.
If your application is accessed by way of a network, then Oracle recommends that you create a virtual internet protocol address for the application as a dependent resource. In the previous example, network1 is an application VIP address. Create application VIP addresses as follows:
crs_profile –create network1 -t application \ -a $CRS_HOME/bin/usrvip \ -o oi=eth0,ov=138.3.83.78,on=255.255.240.0
In this example, $CRS_HOME is the home directory for the Oracle Clusterware installation. In addition, eth0 is the name of the public network adapter, 138.3.83.78 which resolves by way of DNS to a new IP address that will be used to locate your application regardless of the node it is running on. Finally, 255.255.240.0 is the netmask for the public IP address. As the oracle user, register the VIP address with Oracle Clusterware as follows:
crs_register network1
On UNIX-based operating systems, the application VIP address script must run as the root user. As the root user, change the owner of the resource as follows:
crs_setperm network1 –o root
As the root user, enable the oracle user to run this script:
crs_setperm network1 –u user:oracle:r-x
As the oracle user, start the VIP address as follows:
crs_start network1
The placement policy specifies how Oracle Clusterware selects a node on which to start an application and where to relocate the application after a node failure. Only cluster nodes on which all of the required resources are available, as listed in an application's profile, are eligible to be considered as hosting nodes for an application. The Oracle Clusterware supports the following placement policies:
balanced—The Oracle Clusterware favors starting or restarting the application on the node that is currently running the fewest resources. A placement that is based on optional resources is considered first. Next, the host with the fewest resources running is chosen. If no node is favored by these criteria, then any available node is chosen.
favored—The Oracle Clusterware refers to the list of nodes in the HOSTING_MEMBERS attribute of the application profile. Only cluster nodes that are in this list and that satisfy the resource requirements are eligible for placement consideration. Placement due to optional resources is considered first. If no node is eligible based on optional resources, then the order of the hosting nodes determines which node runs the application. If none of the nodes in the hosting node list are available, then Oracle Clusterware places the application on any available node. This node may or may not be included in the HOSTING_MEMBERS list.
restricted—Similar to favored except that if none of the nodes on the hosting list are available, then Oracle Clusterware does not start or restart the application. A restricted placement policy ensures that the application never runs on a node that is not on the list, even if you manually relocate it to that node.
You must specify hosting nodes in the HOSTING_MEMBERS attribute to use a favored or restricted placement policy. Do not specify hosting nodes in the HOSTING_MEMBERS attribute with a balanced placement policy. Otherwise, the application will not validate and you cannot register it. If ACTIVE_PLACEMENT is set to 1, then the placement of the application is re-evaluated whenever you add a node to the cluster or if the cluster node restarts. This enables Oracle Clusterware to relocate applications to a preferred node after the node recovers from a failure. To have Oracle Clusterware relocate an application to a preferred node at a time other than when the node rejoins the cluster, use the REBALANCE attribute to specify a time at which placement can be re-evaluated.
The Oracle Clusterware uses optional resources to choose a hosting node based on the number of optional resources that are in an ONLINE state on the hosting node. If each node has an equal number of optional resources in an ONLINE state, then Oracle Clusterware considers the order of the optional resources as follows:
The Oracle Clusterware compares the state of the optional resources on each node starting at the first resource that you list in the application profile and then proceeds through the list.
For each consecutive resource in your list, if the resource is ONLINE on one node, then any node that does not have the resource ONLINE is not considered.
The Oracle Clusterware evaluates each resource in the list in this manner until only one node is available to host the resource.
The maximum number of optional resources is 58.
If this algorithm results in multiple preferred nodes, then the resource is placed on one of these nodes chosen according to its placement policy.
This section provides the following guidelines for writing Oracle Clusterware action programs that interpret Oracle Clusterware start, stop, and check commands:
The Oracle Clusterware relies on a status code upon exiting from an action program to set the resource state to ONLINE or OFFLINE. On Windows-based systems, the program should be non-blocking, which may imply a Windows service or a Windows resource that does not block during console interactions.
Action programs must return a status code to indicate success or failure. For example, on UNIX-based systems if the script is written in Bourne Shell, then the program should issue exit(1) to indicate failure, and exit(0) to indicate success. Similarly, on Windows-based systems, the action program should return a status of (0) to indicate success and (1) to indicate failure.
After application failure, Oracle Clusterware calls the action program with a check parameter. The action program replies to Oracle Clusterware with a status of (1) to indicate failure. After receiving this failure status, Oracle Clusterware calls the action program with a stop parameter. It is important that the action program returns a status of (0) to indicate a successful stop of the application, even though the application was not running when the stop request was called.
The Oracle Clusterware sets the resource state to UNKNOWN if an action program's stop entry point fails to exit within the number of seconds in the SCRIPT_TIMEOUT value, or if the action program returns with a code that indicates failure. This may occur during a start, relocation, or stop operation. Ensure that the action program's stop entry point exits with a value that indicates success if the resource is successfully stopped or if the resource is not running.
When a daemon or service starts, it usually needs to start as a background process, depending on the platform. However, a resource started in this way always returns success during a start attempt. This means that the default scripts cannot detect failures caused by minor errors, such as misspelled command paths.
On UNIX-based systems, if a resource does not move to the background immediately upon startup, then you can start the application in the background by adding an ampersand (&) to the end of the line that starts the application.
On Windows-based systems, you can use net start to start a service that needs to start in the background.
When using commands to start daemons or services in the background, interactively make test runs of the commands used in the script to eliminate errors before using the script with Oracle Clusterware.
This section describes how Oracle Clusterware runs action programs. The first argument to an action program is the command start, stop, or check depending on which action Oracle Clusterware is running. The second argument is the Oracle Clusterware resource name of the application. This enables a script to determine which instance of the resource that Oracle Clusterware is starting, stopping, or checking.An action program can retrieve any of its Oracle Clusterware resource attributes from the environment by using $_CAA_attribute_name. For example, $_CAA_NAME contains the application name, the second argument to the script, and $_CAA_HOSTING_MEMBERS contains its HOSTING_MEMBERS attribute.
The Oracle Clusterware supports user-defined attributes in Oracle Clusterware applications, which are attributes having names that contain USR. User-defined attributes are stored as part of the Oracle Clusterware application profile for the application. You can reference them in an action program using $_USR_attributename. To add a user-defined attribute, add it to the file CRS home/crs/template/application.tdf using the following syntax:
# # an example user-defined attribute # #!=========================== attribute: USR_EXAMPLE type: string switch: -o example default: required: no
The attribute parameter contains the name of the new attribute. The type parameter defines the type of the user-defined attribute and can be one of the following:
string
boolean
integer—a numeric attribute
positive_integer—a numeric attribute that must be positive
name string
name_list—a comma-delimited list of names
The switch parameter describes how the attribute is specified for the crs_profile command. Set the required field to no for user-defined attributes.
Note:
User-defined attribute names that begin withUSR_ORA are reserved for use by Oracle.This section describes the Windows-based crsuser program. If you create an Oracle Clusterware application, then run the following command:
crsuser add [domain\]username
Provide the user's Windows password. This creates the service OracleCRSToken_user that Oracle Clusterware needs for starting the Oracle Clusterware resources under the given user ID. You can also use the crsuser command remove [domain\]username to remove a token service and crsuser list to list a registered users.
This section describes how to use the Oracle Clusterware commands under the following topics:
Each application that you manage with Oracle Clusterware must have an application profile and the profile must be registered in the OCR. Use the crs_register command to register applications in the OCR. For example, enter the following command to register the mail monitoring application from the previous example:
# crs_register postman
If you modify a profile, then update the OCR by re-running the crs_register -u command.
To start an application resource that is registered with Oracle Clusterware, use the crs_start command. For example:
# crs_start postman
The following text is an example of the command output:
Attempting to start `postman` on node `rac1` Start of `postman` on node `rac1` succeeded.
The application now runs on the node named rac1.
Note:
The name of the application resource may or may not be the same as the name of the application.See Also :
Appendix B, "High Availability Oracle Clusterware Command-Line Reference and C API" for examples of Oracle Clusterware command outputThe command waits for the amount of time specified by the setting for the SCRIPT_TIMEOUT parameter to receive a notification of success or failure from the action program each time the action program is called. Application resources can be started if they have stopped due to exceeding their failure threshold values. You must register a resource with crs_register before you can start it.
To start and resources, use the crs_start and crs_stop commands. Manual starts or stops outside of Oracle Clusterware can invalidate the resource status. In addition, Oracle Clusterware may attempt to restart a resource on which you perform a manual stop operation.
All required resources must be online on the node where you start the resource. If the resources that the REQUIRED_RESOURCES parameter identifies are offline, then the command crs_start resource_name will start the required resources before starting the resource.
Running the crs_start command on a resource sets the resource target value to ONLINE. The Oracle Clusterware attempts to change the state to match the target by running the action program with the start parameter. When a resource is running, both the target state and current state are ONLINE.
Starting an Application on an Unavailable Node
When starting an application on a cluster node that is unavailable, crs_start can give indeterminate results. In this scenario, the start section of the action program is run, but the cluster node fails before notification of the start is displayed on the command line. The crs_start command returns a failure with the error Remote start for resource_name failed on node node_name. The application is actually ONLINE but fails over to another node making the application appear as though it were started on the incorrect node.
If a cluster node fails while you are starting a resource on that node, then check the state of the resource on the cluster by using the crs_stat command to determine the state of that resource.
Use the crs_relocate command to relocate applications and application resources. For example, to relocate the mail monitoring application to the node known as rac2, enter the following command:
# crs_relocate postman -c rac2
Each time that the action program is called, the crs_relocate command waits for the duration identified by the value for the SCRIPT_TIMEOUT parameter to receive notification of success or failure from the action program. A relocation attempt fails if:
The application has required resources that are ONLINE on the initial node
Applications that require the specified resource are ONLINE on the initial node
To relocate an application and its required resources, use the -f option with the crs_relocate command. The Oracle Clusterware relocates or starts all resources that are required by the application regardless of their state.
To stop applications and application resources, use the crs_stop command. Immediately after the crs_stop command completes, the application status converts to OFFLINE. Because Oracle Clusterware always attempts to match a resource's state to its target, the Oracle Clusterware subsystem stops the application. The following example stops the mail application from the example:
# crs_stop postman
The following text is an example of the command output:
Attempting to stop `postman` on node `rac1` Stop of `postman` on node `rac1` succeeded.
You cannot stop an application if the application is a required resource for another online application unless you use the force (-f) option. If you use the crs_stop -f resource_name command on an application that is required by other resources and if those resources are online, then Oracle Clusterware stops the application. In addition, all of the resources that require that application that are online are also stopped.
Note:
The Oracle Clusterware can only stop applications and application resources. The Oracle Clusterware cannot stop network, tape, or media changer resources.The following section explains additional information for controlling how Oracle Clusterware manages restarts. You can prevent Oracle Clusterware from automatically restarting a resource by setting several action program attributes. You can also control how Oracle Clusterware manages the restart counters for your action programs. In addition, you can customize the timeout values for the start, stop, and check actions that Oracle Clusterware performs on action scripts. These topics are described under the following headings:
When a node stops and restarts, Oracle Clusterware starts the instance as soon as the node starts. This may not be desirable because instance startup might fail if system components on which the instance depends, such as a volume manager or a file system, are not running. This is especially true if Oracle Clusterware does not manage the system component resources on which the instance depends. To manage automatic restarts, you can use the AUTO_START attribute to specify whether Oracle Clusterware should automatically start a resource when a node restarts. Valid AUTO_START values are:
always—Causes the resource to restart when the node restarts regardless of the resource's state when the node stopped.
restore—Does not start the resource at restart time if it was in an offline state, such as STATE=OFFLINE, TARGET=OFFLINE, when the node stopped. The resource is restored to its state when the node went down. The resource is started only if it was online before and not otherwise.
never—The Oracle Clusterware never restarts the resource regardless of the resource's state when the node stopped.
Note:
Oracle only supports lower-case values foralways, restore, and never.When a resource fails, Oracle Clusterware restarts the resource for only the number of times specified in the profile attribute RESTART_ATTEMPTS regardless of how often the resource fails. The CRSD process maintains an internal counter to track how often a resource has been restarted. There is a mechanism by which Oracle Clusterware can automatically manage the restart attempts counter based on the stability of a resource. Use the UPTIME_THESHOLD attribute to indicate resource stability.
You can specify the time for the UPTIME_THRESHOLD attribute in different units of measure, such as seconds (s), minutes (m), hours (h), days (d) or weeks (w). Examples of valid values for this attribute are: 7d for seven days, 5h for five hours, 180m for 180 minutes, and so on. Specify the time period as a numeric value and the unit of measure as the last character, s, m, h, d, or w.
After the time period that you have indicated by the setting for UPTIME_THRESHOLD has elapsed, Oracle Clusterware resets the value for RESTART_COUNTS to 0. The Oracle Clusterware can alert you when the value for RESTART_COUNT reaches the value that you have set for RESTART_ATTEMPTS.
Note:
Oracle Clusterware writes an alert to the CRSD log file when the value forRESTART_COUNT reaches the value that you have set for RESTART_ATTEMPTS. The Oracle Clusterware does not write this message to the alert file.Some of the failure scenarios for the RESTART_ATTEMPTS and RESTART_COUNT attributes are:
When a resource keeps restarting—The resource does not meet the uptime threshold criteria and it will be stopped after restarting for the number of attempts set by the value for RESTART_ATTEMPTS.
When a node fails or restarts—The Oracle Clusterware resets the value for RESTART_COUNTER to 0 either when the resource relocates or when it restarts on the same node.
If the crsd process fails—Because both RESTART_COUNT and RESTART_ATTEMPTS are stored in OCR, the behavior is not affected.
If you have a pre-Oracle Database 10g release 2 (10.2) installation, add the release 2 (10.2) attributes to your profiles by doing one of the following:
Modify your resources with the release 2 (10.2) attributes and re-register the resources. This causes the separate timeouts to be effective.
Do not modify your resources. This retains the pre-release 2 (10.2) behavior of using the value in SCRIPT_TIMEOUT as the timeout for all start, stop, and check actions.
To unregister an application or an application resource, use the crs_unregister command. You cannot unregister an application or resource that is ONLINE or required by another resource. The following example unregisters the mail application:
# crs_unregister postman
The unregistration process frees space on the OCR. Additionally, run the crs_unregister command as a clean-up step when a resource is no longer managed by Oracle Clusterware. Generally, you should unregister all permanently stopped applications.
To display status information about applications and resources that are on cluster nodes, use the crs_stat command. The following example displays the status information for the postman application:
# crs_stat postman NAME=postman TYPE=application TARGET=ONLINE STATE=ONLINE on rac2
Enter the following command to view information about all applications and resources in tabular format:
# crs_stat -t
The following text is an example of the command output:
Name Type Target State Host ---------------------------------------------------------------- cluster_lockd application ONLINE ONLINE rac2 dhcp application OFFLINE OFFLINE
Enter the following command to determine:
How many times an application resource has been restarted
How many times an application resource has failed within the failure interval
The maximum number of times that an application or resource can be restarted or fail
The target state of the application or resource and the normal status information
# crs_stat -v
To view verbose content in tabular format, enter the following command:
# crs_stat -v -t
The following text is an example of the command output:
Name Type R/RA F/FT Target State Host ---------------------------------------------------------------------- cluster_lockd application 0/30 0/0 ONLINE ONLINE rac2 dhcp application 0/1 0/0 OFFLINE OFFLINE named application 0/1 0/0 OFFLINE OFFLINE network1 application 0/1 0/0 ONLINE ONLINE rac1
Enter the following command to view the application profile information that is stored in the OCR:
# crs_stat -p
The following text is an example of the command output:
NAME=cluster_lockd TYPE=application ACTION_SCRIPT=cluster_lockd.scr ACTIVE_PLACEMENT=0 AUTO_START=1 CHECK_INTERVAL=5 DESCRIPTION=Cluster lockd/statd FAILOVER_DELAY=30 FAILURE_INTERVAL=60 FAILURE_THRESHOLD=1 REBALANCE= HOSTING_MEMBERS= OPTIONAL_RESOURCES= PLACEMENT=balanced REQUIRED_RESOURCES= RESTART_ATTEMPTS=2 SCRIPT_TIMEOUT=60 ...
Refer to the crs_stat command for more information.
See Also:
Appendix B, "High Availability Oracle Clusterware Command-Line Reference and C API" for detailed information about the Oracle Clusterware commands