Oracle E-Business Suite Release 12.2 introduces Online Patching, a new feature that greatly reduces the downtime that was needed in previous releases for application of Release Update Packs (RUPs), Critical Patch Updates (CPUs), and other patches and bug fixes of various kinds.
Key Features:
- In Release 12.2, all patching operations are carried out while the applications are in use and users are online.
- Patching is performed using the new adop (AD Online Patching) utility.
- A short period of downtime is required, but this amounts to little more than a restart of the services: the time the applications are unavailable is measured in minutes rather than hours, and this can be specified to be at the most convenient time.
Note: The classic patching model is designed to minimize downtime by running as fast as possible, using whatever resources are needed. In contrast, the online patching model is designed to minimize downtime by allowing patching operations to be performed while users remain on the system.
Principles:
In essence, online patching is performed as follows:
- A copy is made of the running system.
- Patches are applied to the copy while users continue to access the running system.
- Transparently to users, the copy becomes the new running system.
- What was the original running system (now obsolete) is deleted.
This introduces the concept of a patching cycle that consists of several phases, in contrast to the model used in previous releases. These phases are denoted prepare, apply, finalize, cutover, and cleanup.
Implementation:
Any mechanism that uses a copy of the running application must take into account that an Oracle E-Business Suite application comprises both code and data, stored in the file system and database.
The file system is the easier of the two to cater for, simply requiring an additional copy to be created and maintained. The resulting dual file system consists of one file system that is used by the running system and another one that is either currently being patched, or (as will be the case for most of the time) standing ready to be patched. The two file systems swap roles at the end of each patching cycle, with the transition between them being managed by AutoConfig.
Creating a copy of the database portion of the running applications system is more complex. It has been accomplished by taking advantage of the Oracle Database 11g R2Edition-Based Redefinition (EBR) feature. This allows an application to efficiently store multiple copies (editions) of its application definition in the same database, and thereby enables online upgrade of the database tier.
The database patch edition only comes into existence during a patching cycle, and becomes the new run edition at end of the cycle. The former database run edition (the old edition) and the obsolete objects it contains are discarded at the end of a patching cycle, and the space reclaimed during the cleanup phase.
Tools:
Patching is performed by running the new adop (AD online patching) tool. This tool invokes the adpatch utility that was run directly in previous releases of Oracle E-Business Suite.
Warning: Running adpatch directly is not supported in an online patching environment, except under explicit instruction from Oracle.
The adop tool orchestrates the entire patching cycle, and can be used to run individual phases as required.
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