Implicit Connection Cache

Implicit Connection Cache called as ICC in Oracle RAC. ICC is an advanced JDBC 3.0–compliant connection cache completion for DataSource, which can position to dissimilar fundamental databases. The cache is facilitated by invoking setConnectionCacheEnabled(true) on OracleDataSource. Cache is generated when the first correlation is demanded from the OracleDataSource. ICC produces and preserves physical connections to the database and enfolds them with logical connection. One cache is enough to service all connection requests, and any number of caches can be generated. Preferably, more than one cache is produced when there is necessitate accessing more than one DataSource. While the ICC creates and preserves physical connections to the database, the Connection Cache Manager creates the cache and administers the connection demands to the cache. ICC provides a number of advantages:

It can be employed with both thin and OCI drivers.

OCI clients can register to accept notifications about RAC high availability occurrences and respond when events occur.

During DOWN event giving out, OCI ceases affected connections at the client.

Eliminates connections from the OCI connection pool and the OCI session pool-the session pool maps each session to a physical connection in the connection pool, and there can be multiple sessions per connection.

Another feature is Fails over the connection if TAF has been arranged. If TAF is not configured, then the client only receives an error.

OCI does not currently handle UP events.

There is a one-to-one mapping between the OracleDataSource instance and the cache. When the application call ups the close()method to close the connection, all connections acquired through the datasource are revisited to the cache for reuse. The cache either returns an existing connection or creates a new connection.

The connection cache holds all properties specified by the JDBC 3.0 connection pool specification. The support for these properties allows the application to fine-tune the cache to maximize the performance for each application.

It also supports a mechanism to recycle and refresh stale connections. This helps refresh old physical connections.

Only one cache manager is present per virtual machine (VM) to manage all the caches. The Oracle Connection Cache Manager provides a rich set of APIs to manage the connection cache.

It provides a connection cache callback mechanism. The callback feature provides a mechanism for users to define cache actions when a connection is returned to the cache, when handling abandoned connections, and when a connection is requested but none is available in the cache.

Public boolean handleAbandonedConnection(OracleConnection oracleConnection, Object 0): This function is called when a connection is abandoned.

Public void releaseConnection(OracleConnection oracleConnection, Object o: This function is called when releasing a connection. 

This mechanism offers the capability for the application to describe the cache performance when the events occur.

It supports user-defined connection attributes that conclude which connections are retrieved from the cache. The user characteristics are a name-value pair and are not validated by the implicit connection cache.

There are two methods can retrieve connections based on these properties:

getConnection(java.util.Properties

cachedConnectionAttributes)

getConnection(java.lang.String user, java.lang.String passwd,

java.util.Properties cachedConnectionAttributes)

What is SSD? How to get Good Performance from SSD?

Memory based disks or Solid state disks (SSD) are based on the concept of RAM disks. However, they are relatively more stable. An SSD is very similar to a standard disk drive and, for most practical purposes, behaves like one. To the host system, an SSD is a disk drive. But an SSD does not store data on magnetic disk media. Instead, it stores data on high density arrays of high speed DRAM memory chips. This eliminates the inherent mechanical delays that come with the need to spin a hard disk and position the read/write heads to execute an I/O request. By eliminating such latencies, SSDs achieve access times much faster than conventional disk drives. 

With most vendors, SSD performance is fast and reliable. An SSD has an integral battery-powered hard-disk drive and associated software continuously backing up its contents. At any moment, typically 81 percent of the data on the SSD is backed up to the hard disk. During power failures, batteries maintain power long enough to back up the rest of the data. In some implementations, backing up the contents onto disk is handled at the hardware level, enhancing performance and reliability further.

For database applications, SSDs provide a viable option for enhancing performance by eliminating variable seek times without compromising availability. Most vendors implement custom versions of the SSD concept. An instance, Sun Microsystems has PrestoServe, a high speed static memory-based storage medium that is backed up by lithium powered batteries. In typical Oracle implementations, small but heavy accessed files, such as online redo logs, Undo data files, can be placed on SSDs.

Most implementations of SSDs incorporate highly resilient fault monitoring during regular operations, which includes continuous header checking and data-retention system monitoring. However, have a chat with your vendor’s technical personnel and ensure that such checks are indeed continuous in your case. Also, have an arrangement with your vendor so that their technical personnel can visit your site and perform data-integrity checks at regular intervals, at least every three or four months. If possible, purchase tools from the vendor to conduct such tests in house, more often if necessary. For more assistance about performance tuning, kindly check our remote dba support services or directly contact us.

What is Oracle Database?

Oracle Database – What is it?

Oracle Database, known more colloquially as simply Oracle, is database management system with a model which relational as well as object-oriented.  This article attempts to clarify in lay-man terms what the Oracle Database system does.

What does the Oracle Database do? - The primary purpose of the Oracle Database is to store collected data and retrieve the same when required. Since, in large companies and organisations, the amount of data is huge and almost unmanageable, the Oracle Database is used very frequently. It also provides multi-user access which allows many users from the same organisation to access the data at the same time without crashes or bugs. Another advantage of having an Oracle Database manage your information is that the data is secure and even if the system crashes, retrieving the data becomes very easy.

How does an Oracle Database Work? : - An oracle database usually contains datafiles which contain and classify the various data in various tables and indices. It stores these datafiles and executes pre-stored functions and procedures. The data is stored typically as tablespaces which are contained in memory segments, extents and data blocks.

To identify and control these various datafiles, the Oracle Database has a control file which essentially records the name and locations of the various files and the time of creation and change. This control file also aids in system data recovery in case of a crash.

The use of a database system makes the management and handling of data extremely simple. It also records the various changes made by multiple users and keeps a record of which changes were made by whom. However, it must be noted that there is a lock on changing and modifying data by other users if one user is already doing so. 

Thus the Oracle Database system is a boon for information and data storage and management in most companies worldwide. Nowadays, Oracle database is most popular RDBMS in global market and Oracle company is also becoming giant. Oracle is having now Sun products like Java, MySQL, Solaris operating system and Sun hardware, Sun storage. Before taken over of Sun Microsys, Oracle didn't have it's own operating system and hardware like IBM DB2 and Microsoft. But now Oracle has everything and it becomes most powerful database, software, hardware company in market. Due to these all reasons, database administrator of Oracle is earning more and DBA services is highly demand-able in market.