Configure Server Environments – Questionnaire 5

• What are the guidelines for the location of CacheDirectory attribute when configuring for high Availability.

  The location of the CacheDirectory attribute should be a local directory, even when configuring for high availability
  

• What happens if the filestore native wlfileio driver cannot be loaded.

  If the file store native wlfileio driver cannot be loaded, the store automatically runs in an alternate specialized Direct-Write policy mode.
  

• Explain Direct-Write policy

  When the Direct-Write policy is selected, WebLogic Server writes synchronously to a primary set of files in the location defined by the Directory attribute of the file store configuration using a native I/O wlfileio driver
  

• Explain Cache-Flush Policy

  When the Cache-Flush policy is selected, WebLogic Server enables the default file write behavior of the operating system and storage device, which typically includes caching and scheduling file writes, but forces a flush of the cache to disk before completing a transaction.
  

• Is Cache-Flush Policy transactionally safe

  It is transactionally safe
  

• What Synchronous Write policy provide lower runtime performance and in what cases

  Tends to provide lower runtime performance than the direct-write policies in typical use cases, except in those cases with large numbers of simultaneous producers or consumers.
  

• Explain Disabled Policy

  When the Disabled policy is selected, WebLogic Server relies on the default file write behavior of the operating system and storage device. In most cases, file writes are cached in memory and are scheduled for writing instead of being directly written to disk.
  

• What are the drawbacks of Disabled policy and why

  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.
  

• When do we see failures in case of Disabled policy

  Simply shutting down an operating system or killing a WebLogic Server process does not generate these failures, as an OS flushes all outstanding writes under these circumstances during a normal shutdown. Instead, these failures can be emulated by abruptly shutting the power off to a busy server.
  

• What does JDBC TLOG store contains and what are its benefits

  JDBC TLOG stores persist transaction logs to a database, which provides the following benefits:
  ■ Leverages replication and HA characteristics of the underlying database.
  ■ Simplifies disaster recovery by allowing the easy synchronization of the state of the database and TLOGs.
  ■ Improved Transaction Recovery service migration as the transaction logs to do not need to be migrated (copied) to a new location.
  

• Can multiple weblogic servers share same JDBC TLOG store

  Only one JDBC TLOG store can be configured per WebLogic Server. Conversely, multiple WebLogic Servers can not share a JDBC TLOG store.
  

• Can JDBC TLOG data store use a data source that supports global transactions

  You cannot use a data source that is configured to use an XA JDBC driver or is configured to support global transactions. Use a non-XA data source.
  

• What is the relationship between database used to store TLOG information and the server startup.

  The database used to store the TLOG information must be available at server startup. If the database is not available, the WebLogic Server instance will fail to boot.
  

• What happens if the database used to store TLOG inforamtion goes down, while weblogic server is running

  If the JDBC TLOG store becomes unavailable, the JTA health state transitions to FAILED and any global transactions will fail. In turn, the server life-cycle changes to FAILED.
  

• What is the status of pending transactions if the TLOG store is changed from one store type to another and from one location to another.

  If the TLOG store is changed from one store type to another or from one location to another, the change takes effect only after reboot and all pending transactions in the old store are not be copied to the new store. You must ensure there are no pending transactions before changing the TLOG store type or location.
  

• What is the default JDBC store database table name

  The JDBC store database contains a database table, named WLStore, that is generated automatically and is used internally by WebLogic Server.
  

• What is the status of JDBC data stores, when the the Database becomes failed or unavailable.

  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.
  TestConnectionsOnReserve=”true”
  TestTableName=”SYSTABLES”
  ConnectionCreationRetryFrequencySeconds=”600″
  

• What is the transaction type when we use JDBC persistent Store

  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.
  

• What is the recommendation to improve performance under heavy JDBC Store I/O loads.

  Under heavy JDBC store I/O loads, you can improve performance by configuring a JDBC store to use multiple JDBC connections to concurrently process I/O operations.
  

• How do you enable I/O Multithreading for JDBC Stores

  To enable I/O multithreading, set the Worker Count attribute to an integer value greater than 1. The default value of this configuration property is 1 and disables this option.
  

• What is the Worker Count attribute

  The Worker Count attribute specifies the number of worker threads the JDBC store uses to process store I/O. Each worker thread acquires one JDBC connection from the configured data source pool when the store is opened.
  

• What is the Oracle recommendation to the Oracle database, when I/O Multithreading is used.

  To reduce contention on Oracle databases, Oracle recommends rebuilding the primary key index into a reverse key index when I/O multithreading is used.
  Oracle recommends reverse indexes for I/O multithreading and non-reverse indexes for single threaded I/O.
  

• At a high level, what are the different systems that can be monitored for a persistent store

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

• What is the criteria for store utility to be executed for Administering Persistent Store

  The store utility operates only on a store that is not currently opened by a running server instance. This utility can be run from a Java command line or from WebLogic Scripting Tool (WLST).
  

• What are the most common use of Store utility for Store Administration.

  The most common uses-cases for store administration are for compacting a file store to reduce its size and for dumping the contents of a file store of JDBC store to an XML file for troubleshooting purposes
  

• What are the limitations of Persistent Store
  • A persistent file store should not be opened simultaneously by two server instances;
    
  • 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.
    
  • A file store may return exceptions when its disk is full.
    
• What is the configuration to be taken care, when multiple servers try to access the same store at the same time.

  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.)