Configuring WebLogic Server Environments

Using the WebLogic Persistent Store

The following sections explain how to configure and monitor the persistent store, which provides a built-in, high-performance storage solution for WebLogic Server subsystems and services that require persistence.

• Overview of the Persistent Store
• Using the Default Persistent Store
• Using Custom File Stores and JDBC Stores
• Creating a Custom (User-Defined) File Store
• Creating a JDBC Store
• Guidelines for Configuring a JDBC Store
• Monitoring a Persistent Store
• Limitations of the Persistent Store

 

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Overview of the Persistent Store

The persistent store provides a built-in, high-performance storage solution for WebLogic Server subsystems and services that require persistence. For example, it can store persistent JMS messages or temporarily store messages sent using the Store-and-Forward feature. The persistent store supports persistence to a file-based store or to a JDBC-enabled database.

Table 6-1 defines many of the WebLogic services and subsystems that can create connections to the persistent store. Each subsystem that uses the persistent store specifies a unique connection ID that identifies that subsystem.

For more information about the store connection IDs, see Monitoring Store Connections.

Features of the Persistent Store

The key features of the persistent store include:

• Default file store for each server instance that requires no configuration
• One store is shareable by multiple subsystems, as long as they are all targeted to the same server instance or migratable target
• High-performance throughput and transactional support
• Modifiable parameters that let you create customized file stores and JDBC stores
• Monitoring capabilities for persistent store statistics and open store connections

High-Performance Throughput and Transactional Support

Throughput is the main performance goal of the persistent store. Multiple subsystems can share the same persistent store, as long as they are all targeted to the same server instance or migratable target.

This is a performance advantage because the persistent store is treated as a single resource by the transaction manager for a particular transaction, even if the transaction involves multiple services that use the same store. For example, if JMS and EJB timers share a store, and a JMS message and an EJB timer are created in a single transaction, the transaction will be one-phase and incur a single resource write, rather than two-phase, which incurs four resource writes (two on each resource), plus a transaction entry write (on the transaction log).

Both the file store and the JDBC store can survive a process crash or hardware power failure without losing any committed updates. Uncommitted updates may be retained or lost, but in no case will a transaction be left partially complete after a crash.

Comparing File Stores and JDBC Stores

The following are some similarities and differences between file stores and JDBC stores:

• The default persistent store can only be a file store.
• A JDBC store cannot be used as a default persistent store.
• The transaction log (TLOG) can only be stored in a file store.
• Both have the same transaction semantics and guarantees. As with JDBC store writes, file store writes are guaranteed to be persisted to disk and are not simply left in an intermediate (that is, unsafe) cache.
• Both have the same application interface (no difference in application code).
• All things being equal, file stores generally offer better throughput than a JDBC store.

Note: If a database is running on high-end hardware with very fast disks, and WebLogic Server is running on slower hardware or with slower disks, then you may get better performance from the JDBC store.

• File stores are generally easier to configure and administer, and do not require that WebLogic subsystems depend on any external component.
• File stores generate no network traffic; whereas, JDBC stores will generate network traffic if the database is on a different machine from WebLogic Server.
• JDBC stores may make it easier to handle failure recovery since the JDBC interface can access the database from any machine on the same network. With the file store, the disk must be shared or migrated.

Securing File Store Data

In order to properly secure file store data, you must set appropriate directory permissions on all your file store directories. If you require data encryption, you must use appropriate third-party encryption software.

High Availability For Persistent Stores

For high availability, a persistent file-based store (default or custom) can be migrated along with its parent server as part of the "server-level" migration feature, which provides both automatic and manual migration at the server-level, rather than on the service level. For more information, see "Server Migration" section of Using WebLogic Server Clusters. However, file-based stores must be configured on a shared disk that is available to the migratable target servers in the cluster.

File-based stores can also be migrated as part of a "service-level" migration for JMS servers and the JTA transaction recovery service, which can be moved from one server to another within a cluster. For more information on service-level migration, see "Service Migration" in Using WebLogic Server Clusters. However, file-based stores must still be configured on a shared disk that is available to the migratable target servers in the cluster.

Therefore, if you have applications that need access to persistent stores that reside on remote machines after the migration of a JMS server or JTA transaction log, then you must implement one of the following highly-available storage solutions:

• File-based stores (default or custom) — Implement a hardware solution, such as a dual-ported SCSI disk or Storage Area Network (SAN) to make a file store available from shareable disks or remote machines.

Note: If a file store is disconnected and re-connected again, its host server instance must be rebooted to successfully continue sending/receiving persistent JMS messages. For example, if for some reason the file system containing a file store is unmounted and then remounted, attempts to send persistent JMS messages will generate JMS exceptions until the host server is rebooted.

• JDBC-accessible stores — Configure a JDBC store and use JDBC to access this store, which can be on yet another server. Applications can then take advantage of any high-availability or failover solutions offered by your database vendor. In addition, JDBC stores support multi data sources, which provide failover between nodes of a highly available database system, such as redundant databases or Oracle Real Application Clusters (RAC). For more information about using JDBC multi data sources, see "Configuring JDBC Multi Data Sources" in Configuring and Managing WebLogic JDBC.
• Any persistent store — Use high-availability clustering software such as VERITAS^TM Cluster Server, which provides an integrated, out-of-the-box solution for BEA WebLogic Server-based applications. Some other recommended high-availability software solutions include SunCluster, IBM HACMP, or the equivalent.

 

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Using the Default Persistent Store

Each server instance, including the administration server, has a default persistent store that requires no configuration. The default store is a file-based store that maintains its data in a group of files in a server instance's data\store\default directory. A directory for the default store is automatically created if one does not already exist. This default store is available to subsystems that do not require explicit selection of a particular store and function best by using the system's default storage mechanism. For example, a JMS Server with no persistent store configured will use the default store for its Managed Server and will support persistent messaging.

The default store can be configured by directly manipulating the DefaultFileStoreMBean parameters. If this MBean is not defined in the domain's configuration file, then the configuration subsystem ensures that the DefaultFileStoreMBean always exists with the default values.

Also, the Administration Console enables you to change the default store parameters, such as its default directory location and Synchronous Write Policy, as described in "Modify the Default Store Settings" in the Administration Console Online Help.

In addition to using the default file store, you can also configure a custom file store or JDBC store to suit your specific needs, as explained in Using Custom File Stores and JDBC Stores. One exception, however, is the transaction log (TLOG), which always uses the default store. This is because the transaction log must always be available early in the server boot process.

Default Store Location

The default store maintains its data in a data\store\default directory inside the servername subdirectory of a domain's root directory

For example, if no directory name is specified for the default file store, it defaults to:

bea_home\user_projects\domains\domain-name\servers\server-name\data\store\default

where domainname is the root directory of your domain, typically c:\bea\user_projects\domains\domainname, which is parallel to the directory in which WebLogic Server program files are stored, typically c:\bea\weblogic90.

You can, however, specify another location for the default store by directly manipulating the DefaultFileStoreMBean parameters or by using the Administration Console, as described in "Modify the Default Store Settings" in the Administration Console Online Help.

Example of a Default File Store

Here's an example of how a default file store may look in a domain's configuration file, with the default directory location and Synchronous Write Policy settings overridden:

<server>
  <name>myserver</name>
  <default-file-store>
  <directory>C:/store</directory>
  <synchronous-write-policy>Disabled</synchronous-write-policy>
  </default-file-store>
</server>

 

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Using Custom File Stores and JDBC Stores

In addition to using the default file store, you can also configure a file store or JDBC store to suit your specific needs. A custom file store, like the default file store, maintains its data in a group of files in a directory. However, you may want to create a custom file store so that the file store's data is persisted to a particular storage device. When configuring a file store directory, the directory must be accessible to the server instance on which the file store is located.

A JDBC store can be configured when a relational database is used for storage. A JDBC store enables you to store persistent messages in a standard JDBC-capable database, which is accessed through a designated JDBC data source. The data is stored in the JDBC store's database table, which has a logical name of WLStore. It is up to the database administrator to configure the database for high availability and performance.

For more information about configuring a persistent store, see When to Use a Custom Persistent Store.

When to Use a Custom Persistent Store

WebLogic Server provides configuration options for creating a custom file store or JDBC store. For example, you may want to:

• Place a file store's files on a particular device.
• Use a JDBC store rather than a file store for a particular server instance.
• Allow all physical stores in a cluster to share the same logical name.
• Logically separate different services to use different files or tables. (This may simplify administration and maintenance at the expense of reduced performance.)

Methods of Creating a Persistent Store

A customized persistent store can be configured in the following ways:

• Use the Administration Console to configure a custom file store or JDBC store, as described in "Configure Persistent Stores" in the Administration Console Online Help.
• Directly edit the configuration file (config.xml) of the server instance that is hosting the default persistent store.
• Use the WebLogic Java Management Extensions (JMX) to create persistent stores. JMX is the J2EE solution for monitoring and managing resources on a network. For more information see, "Developing Custom Management Utilities with JMX".
• Use the WebLogic Scripting Tool (WLST) to create persistent stores. WLST is a command-line scripting interface that you use to interact with and configure WebLogic Server instances and domains. For more information, see "WebLogic Scripting Tool".
• Use the WebLogic Configuration Wizard to change the options of the default persistent store. For detailed information on how to use the Configuration Wizard to configure a persistent store, see "Creating a New WebLogic Domain".

 

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Creating a Custom (User-Defined) File Store

The following sections provide an example of a custom file store and configuration guidelines for choosing a synchronous write policy.

To create a custom file store, you can directly modify the default FileStoreMBean parameters. For instructions on using the Administration Console to create a custom file store, see "Create File Stores" in the Administration Console Online Help.

Main Steps for Configuring a Custom File Store

The main steps for creating a custom file store are as follows:

Create a directory where the file store's data will be persisted.
Create a custom file store and specify the directory location that you created.
Associate the custom file store with the subsystem(s) that will be using it, such as:
• For JMS servers, select the custom file store on the General Configuration page.
• For Store-and-Forward agents, select the custom file store on the General Configuration page.

Example of a Custom File Store

Here's an example of how a custom file store may look in a domain's configuration file with its files kept in a /disk1/jmslog directory.

<file-store>
  <name>SampleFileStore</name>
  <target>myserver</target>
  <directory>/disk1/jmslog</directory>
</file-store>

Table 6-2 briefly describes the file store configuration parameters that can be modified.

For instructions on configuring a custom file store using the Administration Console, see "Create file stores" in the Administration Console Online Help.

Guidelines for Configuring a Synchronous Write Policy

With the default Synchronous Write Policy of Direct-Write, file store writes are written directly to disk for Solaris and Windows operating systems. This option generally performs faster than the Cache-Flush option.

Changing the default policy to Disabled generally improves file store performance, often quite dramatically, but at the expense of possibly losing sent messages or generating duplicate received messages (even if messages are transactional) in the event of an operating system crash or a hardware failure. This is because transactions are complete as soon as their writes are cached in memory, instead of waiting for the writes to successfully reach the disk. Simply shutting down an operating system does not generate these failures, as an OS flushes all outstanding writes during a normal shutdown. Instead, these failures can be emulated by abruptly shutting the power off to a busy server.

 

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Creating a JDBC Store

The following sections provide an example of a JDBC store, and information about creating a database table for a JDBC store, either using existing DDL or It also includes instruction on enabling Oracle blob record columns in a DDL file.

To create a JDBC store, you can directly modify the default JDBCStoreMBean parameters. For instructions on using the Administration Console to create a JDBC store, see "Create JDBC Stores" in the Administration Console Online Help.

For configuration guidelines on using prefixes with JDBC stores and recommended JDBC data source settings, see Guidelines for Configuring a JDBC Store.

Main Steps for Configuring a JDBC Store

The main steps for creating a JDBC store are as follows:

Create a JDBC data source or multi data source to interface with the JDBC store.
Create a JDBC store and associate it with the JDBC data source or multi data source.
It is highly recommended that you configure the Prefix option to a unique value for each configured JDBC store table.
Associate the JDBC store with the subsystem(s) that will be using it, such as:
• For JMS servers, select the JDBC store on the General Configuration page.
• For Store-and-Forward agents, select the JDBC store on the General Configuration page.

Example of a JDBC Store

Here's an example of how a JDBC store may look in the configuration file, using the JDBC data source MyDataSource, and with a logical name specified:

<jdbc-store>
  <name>SampleJDBCStore</name>
  <target>yourserver</target>
  <data-source>MyDataSource</data-source>
  <logical-name>Baz</logical-name>
</jdbc-store>

Table 6-3 describes the JDBC store configuration parameters that can be modified.

For instructions on configuring a JDBC store using the Administration Console, see "Create JDBC stores" in the Administration Console Online Help.]

Supported JDBC Drivers

When using a JDBC store, the backing database can be any database that is accessible through a JDBC driver. WebLogic Server detects some drivers for supported databases.

For each of these databases, there are corresponding DDL (data definition language) files within the WL_HOME\server\lib\weblogic.jar file, in the weblogic/store/io/jdbc/ddl directory, where WL_HOME is the top-level directory of your WebLogic Server installation.

The DDL files are actually text files containing the SQL commands (terminated by semicolons) that create the JDBC store's database table (WLStore). Therefore, if you are using a database that is not included in this list, you can copy and edit any one of the existing DDL files to suit your specific database, as described in Creating a JDBC Store Table Using a Custom DDL File.

Automatically Creating a JDBC Store Table Using Default and Custom DDL Files

The JDBC Store Configuration page provides an optional Create Table from DDL File option, through which you can access a pre-configured DDL file that is used to create the JDBC store's backing table (WLStore). This option is ignored when the JDBC store's backing table already exists. It is mainly used to specify a custom DDL file created for an unsupported database, or when upgrading JMS JDBC store tables from a prior release to a current JDBC Store table.

If a DDL file name is not specified in the Create Table from DDL File field, and the JDBC store detects that its backing table does not already exist, the JDBC store automatically creates the table by executing a pre-configured DDL file that is specific to the database vendor (see Supported JDBC Drivers).

If a DDL file name is specified in the Create Table from DDL File field, and the JDBC store detects that its backing table does not already exist, the JDBC store searches for the specified DDL file in the file path first, and then, if not found, searches for the DDL file in the CLASSPATH. Once found, the SQL within the DDL file is executed to create the JDBC store's backing table. If the configured file is not found and the table doesn't already exist, the JDBC store will fail to boot.

Creating a JDBC Store Table Using a Custom DDL File

To use a different database from those listed in Supported JDBC Drivers, you can copy and edit any one of the existing DDL template files to suit your specific database.

Use the JAR utility supplied with the JDK to extract the DDL files to the /weblogic/store/io/jdbc/ddl directory using the following command:

jar xf weblogic.jar /weblogic/store/io/jdbc/ddl

Note: If you omit the weblogic/store/io/jdbc/ddl parameter, the entire jar file is extracted.

Edit the DDL file for your database. An SQL command can span several lines and is terminated with a semicolon (;). Lines beginning with pound signs (#) are comments.
Save your changes and rename the new DDL appropriately (for example, mydatabase.ddl)
Create a JDBC store, as explained in "Create JDBC Stores" in the Administration Console Online Help.
Use the Create Table from DDL File option on the General Configuration page to specify your custom DDL file (for example, /mydatabase.ddl

Note: On Windows systems, for full path names always include the drive letter.

Enabling Oracle BLOB Record Columns

For Oracle databases, you can use the oracle_blob.ddl file to create a JDBC store table with a BLOB record column type rather than the default LONG RAW record column type. The oracle_blob.ddl file is pre-configured and supplied in the WebLogic CLASSPATH, as described in Supported JDBC Drivers.

To use the Oracle BLOB DDL with a JDBC store:

Shut down the server instance that uses the JDBC store.
Delete the current JDBC table, as explained in Managing JDBC Store Tables.
Reboot the server instance.
Create a new JDBC store, as explained in "Create JDBC Stores" in the Administration Console Online Help.
In the Create Table from DDL File field on the General Configuration page, enter the location of the oracle_blob.ddl file, as follows: /oracle_blob.ddl
Click Finish to create the JDBC store's backing table.

If you need to preserve data already in a Oracle LONG RAW column, but still want to switch the column to BLOB, do not use this method. Instead, consult the Oracle documentation for the SQL ALTER TABLE command.

Managing JDBC Store Tables

The JDBC utils.Schema utility allows you to regenerate a new JDBC store database table (WLStore) by deleting the existing version. Running this utility is usually not necessary, since WebLogic Server automatically creates this table for you. However, if your existing JDBC store database table somehow becomes corrupted, you can delete it using the utils.Schema utility.

The utils.Schema utility is a Java program that takes command-line arguments to specify the following:

• JDBC driver
• Database connection information
• Name of a file containing the SQL Data Definition Language (DDL) commands that create the database table

Using the utils.Schema Utility to Delete a JDBC Store Table

Enter the utils.Schema command, as follows:

$ java utils.Schema url JDBC_driver [options] DDL_file

Note: To execute utils.Schema, your CLASSPATH must contain the weblogic.jar file.

Table 6-5 lists the utils.Schema command-line arguments.

For example, the following command deletes a JDBC table named MYWLStore in an Oracle server named DEMO, with the user name user1 and password foobar:

$ echo "drop MYWLStore;" > drop.ddl

$ java utils.Schema 
jdbc:weblogic:oracle:DEMO \
weblogic.jdbc.oci.Driver -u user1 -p foobar -verbose \
drop.ddl

 

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Guidelines for Configuring a JDBC Store

The following sections provide guidelines for using JDBC store prefixes, recommended WebLogic JDBC data source settings for JDBC stores, and handling JMS transactions with JDBC stores.

Using Prefixes with a JDBC Store

The JDBC store database contains a database table, named WLStore, that is generated automatically and is used internally by WebLogic Server. The JDBC store provides an optional Prefix Name parameter, which can be used to provide more precise access to the database table.

It is always a best practice to configure a prefix for the JDBC WLStore table name, especially when:

• The database requires fully-qualified names. (You should verify this with your database administrator.)
• There is more than one JDBC store instance sharing a database, since no two JDBC stores can share the same table.
• There are many tables in the database. Setting the prefix reduces the number of tables the JDBC store must search through to find its table during boot.

JDBC Store Table Rules

To avoid potential data loss, follow these rules:

• Each JDBC store table name must be unique.
• If multiple JDBC stores share a table, the behavior is undefined and data loss is likely.
• There is no procedure for combining two database tables into a single table.

Prefix Name Format Guidelines

For most databases, the Prefix Name option for the JDBC store's backing database table should be set in the following format for each configured JDBC store, which will result in a valid table name when prepended to the JDBC store table name:

[[[catalog.]schema.]prefix]

Note that each period in the [[[catalog.]schema.]prefix] format is significant. Generally, catalog identifies the set of system tables being referenced by the DBMS, and schema generally corresponds to ID of the table owner (username). When no prefix is specified, the JDBC store table name is simply WLStore and the database implicitly determines the schema according the current user of the JDBC connection.

For example, in a production database, the database administrator could maintain a unique table for the Sales department, as follows:

[[[Production.]JMSAdmin.]Sales]

The resulting table will be created in the Production catalog, under the JMSAdmin schema, and will be named SalesWLStore.

For some DBMS vendors, such as Oracle, there is no catalog to set or choose, so the format simplifies to [[schema.]prefix]. For more information, refer to your DBMS documentation for instructions on fully-qualified table names, but note that the syntax specified by the DBMS may differ from the format required for this option.

Caution: If the Prefix Name setting is changed, but the WLStore database table already exists in the database, take care to preserve existing table data. In this case, the existing database table must be renamed by a database administrator to match the new configured table name.

Recommended JDBC Data Source Settings for JDBC Stores

The following settings are recommended when you use a JDBC data source or multi data source for JDBC stores.

Automatic Reconnection to Failed Databases

WebLogic Server provides robust JDBC data sources that can automatically reconnect to failed databases after they come back online, without requiring you to restart WebLogic Server. To take advantage of this capability, and make your use of JDBC stores more robust, configure the following options on the JDBC data source associated with the JDBC store:

TestConnectionsOnReserve="true"
TestTableName="SYSTABLES"
ConnectionCreationRetryFrequencySeconds="600"

For more information about JDBC default Test Table Names, see "Connection Testing Options for a Data Source" in the Configuring and Managing WebLogic JDBC. For more information about setting the number of database reconnection attempts, see the "Enabling Connection Creation Retries" section in Configuring and Managing WebLogic JDBC.

Required Setting for WebLogic Type 4 JDBC DB2 Drivers

For data sources used as a JDBC store that use the WebLogic Type 4 JDBC driver for DB2, the BatchPerformanceWorkaround property must be set to "true" due to internal JMS batching requirements.

For more information, see the "Performance Workaround for Batch Inserts and Updates" section in the WebLogic Type 4 JDBC Drivers documentation.

Handling JMS Transactions with JDBC Stores

You cannot configure a JDBC store to use a JDBC data source that is configured to support global transactions. The JDBC store must use a JDBC data source that uses a non-XA JDBC driver. You also cannot enable Logging Last Resource or Emulate Two-Phase Commit in the data source.

Because the JDBC store implements the XAResource interface, it acts as it's own resource manager and handles the transactions above the JDBC driver level. That is, the store itself implements the XAResource and handles the transactions without depending on the database (even when the messages are stored in the database).

This means that whenever you are using a JDBC store and a database (even if it is the same database where the JMS messages are stored), then it is two-phase commit transaction.

For more information about using JMS transactions with a JDBC store, see "Using Transactions with WebLogic JMS" in Programming WebLogic JMS.

From a performance perspective, you may also boost your performance as follows:

• Ensure that the JDBC data source used for the database work exists on the same server instance as the JMS destination—the transaction will still be two-phase, but it will be handled with less network overhead.
• Use file stores rather than JDBC stores.
• Configure multiple services to share the same store if they will commonly be invoked within the same transaction.
• If an application directly performs database operations in addition to invoking store services (such as JMS) within the same transaction, consider using a JDBC data source with Logging Last Resource (LLR) enabled for the database operations.

With the LLR optimization, the transaction will follow the two-phase commit protocol, but the database operations will be handled in a single local transaction, which may improve overall transaction performance. For more information on using the LLR optimization, see "Understanding the Logging Last Resource Transaction Option" in Configuring and Managing WebLogic JDBC.

 

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Monitoring a Persistent Store

You can monitor statistics for each existing persistent store and for each open store connection.

Monitoring Stores

Each persistent store is represented at runtime by an instance of the PersistentStoreRuntimeMBean, which provides the following options.

Monitoring Store Connections

For each open persistent store connection, the persistent store also registers a PersistentStoreConnectionRuntimemMBean, which provides the following options.

Table 6-8 defines most of the runtime prefix names of the WebLogic services and subsystems that can create a connection to the persistent store.

 

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Limitations of the Persistent Store

The following limitations apply to the persistent store:

• A persistent file store should not be opened simultaneously by two server instances; otherwise, there is no guarantee that the data in the file will not be corrupted. If possible, the persistent store will attempt to return an error in this case, but it will not be possible to detect this condition in every case. It is the responsibility of the administrator to ensure that the persistent store is being used in an environment in which multiple servers will not try to access the same store at the same time. (Two file stores are considered the "same store" if they have the same name and the same directory.)
• Two JDBC stores must not share the same database table, because this will result in data corruption.
• A persistent store may not survive arbitrary corruption. If the disk file is overwritten with arbitrary data, then the results are undefined. The store may return inconsistent data in this case, or even fail to recover at all.
• A file store may return exceptions when its disk is full. However, it will resume normal operation by no longer throwing an exception when disk space has been made available. Also, the data in the persistent store must remain intact as described in the previous points.

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