How Oracle databases are patched

Patching the software is equivalent to giving people a vaccination, which is critical to the stable operation of the system. This paper introduces the classification, installation and management of Oracle database patches in detail and systematically.

The software patches that vendors provide to users are in the form of compiled library functions, so installing software patches actually copies these library functions to the appropriate directory and joins them when needed. Software companies typically organize all patches for a release after a period of time: merge, resolve conflicts, conduct overall testing, and automate file copy and join operations to get a software patch "package". Different companies use different names, and the Windows Service Pack, which is now familiar to general computer users, is a patch package. The name of the patch package given by Oracle company is patch set, and the version after installing patch set is called Patch set Release (PSR).

Oracle companies provide PSR on a regular basis to products that are in standard technical support, such as when completing this article, The newest PSR of version 10.2 is 10.2.0.2; The newest PSR of version 10.1 is 10.1.0.5; the latest (and most likely final) PSR of version 9.2 is 9.2.0.8.

The corresponding patch will certainly be included in the next PSR when a newly discovered bug is installed after the latest PSR. PSR is cumulative, that is, the next PSR will include patches for all patches and newly discovered bugs in the current PSR. When there are several PSR at the same time, only the latest version can be installed once. However, since the issue of PSR has a certain interval, if these bugs have a greater impact on users, Oracle will also expose and provide these patches to users, which are called individual patches (interim Patch,one-off Patch or Patch Set Exception). For a final patch release, the individual patches become the only option when new bugs that affect the system are found because no longer have the next PSR.

In addition, Oracle also regularly publishes security patches, called CPUs (Critical Patch Updates). Security patches are used to fix software vulnerabilities (vulnerability) or commonly said security breaches. This kind of problem does not belong to the software error, in normal use does not appear any problem. But people with ulterior motives can circumvent the security management mechanism of the database system and achieve the purpose of unauthorized access by running very cleverly designed code.

In addition there is a kind of patch: Diagnostic patch (Diagnostic patch). As the name suggests, this kind of patch is not used to solve the problem, but to find the cause of the problem. This type of patch only needs to be installed when the Oracle Technical Support department requires installation. After you get the diagnostic information you need, you should uninstall the patch immediately.

Pros and cons of timely machine selection

DBAs who manage databases that support large application systems can easily understand the cost of installing software patches. Installing PSR requires stopping the database service, shutting down the database, and scheduling such downtime for many application systems is a difficult task in itself. In fact, more serious is that the installation of PSR May "introduce" new bugs, but affect the normal operation of the application system. Software patches are supposed to fix bugs, how can they bring new bugs? Although some are inconceivable, but unfortunately this is the reality.

For each PSR, there are fewer than hundreds of revisions of the thousands of serious bugs. Even so, after the PSR is released, new problems will soon be discovered in the database after the PSR is installed. Some of these bugs have been around for a while but have not been discovered before, and are now occasionally discovered, or because PSR fixes an error to "activate" it or find it easier. But there are some bugs that are caused by this PSR, which Oracle technical support calls a retrograde step (regression). For each PSR, there are two important documents in the Metalink, one is "list of fixes added in XXXX", which is the list of bugs that the PSR fixes, is a "merit book"; the other is "known issues and alerts Affecting XXXX, is the installation of PSR found after the problem, you can call it a "penance book." Because of the complexity of large software, bugs are almost inevitable. It is important to be able to provide information in a timely manner, and DBAs can make the right judgments in the context of their own systems. Readers do not have to lose confidence in Oracle database products because they know that there are still bugs. The vast majority of the thousands of bugs that PSR fixes are in situations where there are rare environments, or where complex combinations of several components are used.

If there is a problem with the system running, the Oracle technical support or third party experts confirm that the reason is a bug in PSR, so it must be installed as soon as possible, and the components or functions involved in the problem that the PSR has discovered, such as logical Standby , Jvm,rac, etc.) is not used in the system, at which point you can choose to install or choose not to install.

Another factor to consider is the timing of the patch installation. An important prerequisite for these considerations is that the system has been put into operation to worry about "backwards" bugs affecting the system. If the system is still in the development and testing phase, there is no need to hesitate to install the latest PSR, and on this basis to test the application system is working properly. If an exception is found, ask Oracle Technical support to confirm the new bug in a timely manner, and if so, provide an individual patch. The goal is to test the application system on a database platform that is as robust as possible. We can generalize this kind of installation patch strategy as "patch fix new not old".

All of these are for the PSR installation, for individual patches, because the patch fixes a single bug, easy to determine whether the need to install. Note that if several individual patches are installed on top of the current PSR, then after the next PSR is released, all individual patches need to be uninstalled before the next PSR is installed. For ease of management, Oracle Technical Support now requires that tools be opatch to install and manage individual tools, while minimizing manual copying of files.

Finally, the security patch installation is judged. Although the term security vulnerability seems to be very serious, but also to calm the comprehensive analysis of these vulnerabilities in the system harm degree. In fact, the risk of not installing a security patch may be far less than the "standard default" practice of consistently using user names and passwords, which everyone knows Scott/tiger.

Install PSR

Using the Oui tool to install the PSR requires only a few choices with the mouse to enter the automatic execution phase, the process itself is very simple. However, if the requirement must be successful at one time, the operation must be completed at the limited downtime of 2 o'clock in the morning to 4, the installation process is not wrong, and the possibility of this error can be completely ruled out in the future when the problem arises, then some preparatory work needs to be done before starting oui.

1. Information collection

One of the most important documents about PSR is the software patch description, which is equivalent to the installation Guide and release notes in the technical Manual. The file itself is included in the downloaded software patch file, and the filename is patchnote.htm or readme.html. One issue to note is that the patch Set notes found in a software patch file may not be the latest version, You can retrieve the latest version in Metalink based on the prompts in the file.

The other two important documents are the "merit book" and the "Penance book" mentioned earlier, and should read every item of the "Penance book" more carefully than the "merit book". In addition, some of the issues that arise after installing PSR are listed in the patch Set notes Known issues (known Issues) section.

In addition to these three main documents, it should also be searched in Metalink to find out whether there are other technical articles related to this PSR, to find other users to install this PSR or after the installation of the problem of the rescue post, the precedent should be more attention.

2. Making Judgments

After careful reading of the collected articles, according to the actual situation of their own system, make the immediate installation of PSR, or wait for the next PSR decision. If you are suspending the installation, log the reason so that you can track the repair process for the bug later.