This preface lists changes in Oracle Database 2 Day + Real Application Clusters Guide.
The following are changes in Oracle Database 2 Day + Real Application Clusters Guide for Oracle Database 12c Release 1 (12.1).
The following features are new in this release:
Oracle Enterprise Manager Database Express replaces Oracle Enterprise Manager Database Control (DB Control)
In previous Oracle Database releases, DB Control was the primary database management tool described in this manual. DB Control is not included in this release.
Oracle Home User Support for Oracle Database
Starting with Oracle Database 12c Release 1 (12.1), Oracle Database supports the use of an Oracle Home User, which can be specified at installation time. The Oracle Home User can be a Built-in Account or a Windows User Account. If you specify a Windows User Account, then the user should be a low privileged (non-Administrator) account to ensure that the Oracle Home User has a limited set of privileges. Using an Oracle Home User ensures that Oracle Database services have only those privileges required to run Oracle products.
Application Continuity
Application Continuity attempts to mask outages from end users and applications by recovering requests following recoverable outages, unplanned and planned. Application Continuity performs this recovery beneath the application so that the outage appears to the application as a delayed execution. Application Continuity masks recoverable outages - those in which requests would succeed if they were re-issued. Examples include system failures, network disconnects, foreground failures, and storage failures.
Transaction Guard
Before Oracle Database 12c Release 1 (12.1), it was difficult for a database application to recover after an outage, because the commit message that Oracle Database (the server) returned to the application (the client) was not persistent. If the connection between Oracle Database and the application broke or if the database session became unavailable, then the application received a disconnection error message. After an outage, if an application user resubmitted an in-flight transaction that had been committed, then duplicate transactions resulted.
The Oracle Database feature Transaction Guard ensures that each transaction executes at most once. Its PL/SQL interface, the DBMS_APP_CONT.GET_LTXID_OUTCOME procedure, enables an application to determine the outcome of the in-flight transaction after an outage and then recover any work that was lost due to the outage.
Java and JDBC Support for Application Continuity
Application Continuity for Java is available with Oracle Database, JDBC Thin driver, and the Oracle connection pools: UCP (Universal Connection Pool) and WebLogic Server Active GridLink.
Application Continuity is transparent for Java EE and Java SE applications that use Oracle JDBC, use Oracle connection pools (UCP or WLS Active GridLink), and do not have external actions. For applications with external actions (for example, using autonomous transactions or using UTL_HTTP to issue an SOA call), Application Continuity is transparent only if the application's correctness is preserved when these external actions are replayed after a failure.
Oracle JDBC Support for Transaction Guard
Some features previously described in this document are desupported in Oracle Database 12c Release 1 (12.1). See Oracle Database Upgrade Guide for a list of desupported features.