以下部分内容来自patchset文档。
Oracle Database Patch Set Notes 11gRelease 2 (11.2.0.3) Patch Set 2 E24903-01
Patch Set Overview
Oracle Database patch set, release 11.2.0.3 is a full installation of the Oracle Database software. This means that you do not need to install Oracle Database 11gRelease 2 (11.2.0.1) before installing Oracle Database 11gRelease 2 (11.2.0.3).
See Also:
“Oracle Database 11gRelease 2 (11.2.0.3) New Features” inOracle Database New Features Guide
Note the following changes with the new patch set packaging:
New installations consist of installing the most recent patch set, rather than installing a base release and then upgrading to a patch release.
Direct upgrades from previous releases to the most recent patch set are supported.
Out-of-place patch set upgrades recommended, in which you install the patch set into a new, separate Oracle home. In-place upgrades are supported, but not recommended.
11.2.0.3 (包括Oracle 11.2.0.2)的patchset都是完整的安装包，因此可以直接用来安装。
In-Place Upgrade
This feature enables you to upgrade an existing installation of Oracle database to Oracle Database 11gRelease 2 (11.2.0.3) into the same Oracle home directory by replacing the existing database files. The patch set application requires more downtime and is not recommended. This upgrade type requires less disk space.
Note:
If you select In-place upgrade to upgrade Oracle database to the latest version, then you must:
Review “Optionally Performing an In-Place Upgrade (Into the Same Oracle Home)” inOracle Database Upgrade Guide.
Take a complete backup of your Oracle home directory before you perform. the upgrade.
将升级文件安装到原来的Oracle home目录，这样可以节省磁盘空间，但是需要更多的停机时间，这种方法Oracle并不推荐。
Out-of-Place Upgrade
This feature enables you to install Oracle Database 11gRelease 2 (11.2.0.3) in a new, separate Oracle home directory. After the installation is complete, the data from the database in the old Oracle home directory is migrated to the database in the new Oracle home directory.
Out-of-place upgrade process is similar to Oracle database upgrade from one version to another and is the recommended type. The benefits of this upgrade type is that the patch set application requires much less downtime, and is safer when the patch set application must be aborted. This upgrade type requires more disk space to accommodate two Oracle home directories simultaneously.
可以将Oracle Database安装的新的OracleHome目录，当安装结束后，，旧的database会迁移到新的Oracle HOME目录。
这种方法是oracle推荐的方式，它可以降低停机时间，也相对更安全。但是这种方法需要至少两倍的磁盘空间。
更多Oracle相关信息见Oracle 专题页面 ?tid=12