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Link checker errors advice

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Introduzione

Here is some brief advice on some of the common errors reported.  

 Note: Errors that occur in the Link Checker, but not when manually checked with a browser,may relate to the time that the Link Check process is run or may be caused by overloading the target server. Other explanations might be:

  • The browser is quietly “correcting” the URL
  • The browser can handle more types of media (eg: Flash Video) than the link checker
  • The browser is being verified by the target site in order to prevent search engines such as Google indexing the target page
  • The DNS configuration on the database server differs from that of the PC running the browser

Some URLs which are valid in a web browser will never check OK using Link Checker for reasons that can only be resolved by the hosting web server (see below for further details). In these cases it may be useful to set the specific object's Link Checker Frequency to "Never", so that Link Checker never tries to check it.

Common errors reported

ORA-29024: Certificate validation failure -Oracle Database administrator remedy required (OLIB root certificates update).

ORA-12545: Connect failed because target host or object does not exist -check the URL using a browser.

ORA-12570: TNS:packet reader failure -potential network stability issue.

ORA-12547: TNS:lost contact –this potentially indicates that the URL connects to a server process & this is not allowed using the search.

ORA-29259: End-of-input reached.

ORA-29264: Unknown or unsupported URL scheme (eg: htp ? http:www. ?)

ORA-29268: HTTP client error 400 -Bad Request -check the URL using a browser.

ORA-29268: HTTP client error 403 -Forbidden (The server denied the specified Uniform Resource Locator (URL). Contact the server administrator. ) - check the URL using a browser.

ORA-29268: HTTP client error 404 -Not Found -check the URL using a browser.

ORA-29268: HTTP client error 415 -UNSUPPORTED MEDIA TYPE -check the URL using a browser

ORA-29269: HTTP server error 500 -Internal Server Error

ORA-29024: Certificate validation failure -the URL is directing us to an SSL site & there is either no certificate path for this site or it has expired - these are held in the Oracle Wallet Manager. If trusted, the topmost (or "root") certificate for the site should be imported into the Oracle Wallet file. Please contact your regional OCLC support desk for an update to the root certificate file. They will need to know the URL that causes this problem.

ORA-12545: Connect failed because target host or object does not exist - typically the URL is referring to a website that either doesn't exist, has moved or there is simply a typo in the object's LOCATOR field -check the URL using a browser.  Note: Web servers can correct some formatting errors presented by browser sessions in the URL but will not do the same for Link Checker, hence if a site displays OK in a browser but is giving this error in Link Checker look for simple formatting errors (eg. the use of \'s rather than /'s in the URL.)
Occasionally a site returns this intermittently, which may relate to activity on the site at the time of the search & there are also some that consistently return this code although the URL is valid, this is a rare occurrence & cannot be resolved without intervention by the administrators of the target web server.
There are also certain web servers that will return this error for some URLs but not others dependent on the format of the URLs – check if other URLs from the web server are checking OK, change the format of the URL to match ones that do check OK, ensure that it still goes to the same page & that it then checks OK.
If this error is returned for the “Control URL”, then it is possible that the DNS configuration on the database server is not referring to the correct servers in order to obtain the IP address of the target site.

ORA-12547: TNS:lost contact –this potentially indicates that the URL connects to a server process & this is not allowed using the search. This is an issue specific to the web server & cannot be resolved without intervention by the administrators of the target web server.

ORA-12570: TNS:packet reader failure -there could be several reasons for this, it could be that there was a database/network issue at the time of the check. Looking in the database alert log may give some further indication. If a web server consistently returns this error, they may be preventing the search - this is an issue specific to the web server & cannot be resolved without intervention by the administrators of the target web server.

ORA-29259: End-of-input reached -this indicates that the test is being terminated by the remote site, typically if/when testing the link in a browser it takes you to an authentication screen, there is a strong possibility that the site has security in place to prevent such unauthenticated tests. There is no scope to add username and password for each site for link checking purposes at this time in order to overcome this error.

ORA-29264: Unknown or unsupported URL scheme -this indicates that there is something wrong with the syntax of the URL(e.g., htp://www.oclc.org or "Available online at http://www.oclc.org".)

ORA-29268: HTTP client error 400 -Bad Request -there can be several reasons for this error, though basically the remote site is not able to interpret the http request -check the URL in a browser for errors with syntax, possible authentication requirements or subsequent errors reported by the remote site.

ORA-29268: HTTP client error 403 -Forbidden (The server denied the specified Uniform Resource Locator (URL). Contact the server administrator.) - This could mean that authentication is required by the target web server in order to allow verification of the link correctly -check the URL using a browser. There is no scope to add username and password for each site for link checking purposes at this time in order to overcome this error.

ORA-29268: HTTP client error 404 -Not Found -typically the URL is referring to a website that either doesn't exist, has moved or there is simply a typo in the object's LOCATOR field -check the URL using a browser. Occasionally URLs from a web server persistently return this error to Link Checker but can be accessed in a browser, this is an issue specific to the web server & cannot be resolved without intervention by the administrators of the target web server.

ORA-29268:  HTTP client error 415 -UNSUPPORTED MEDIA TYPE -there can be several reasons for this error but there is some sort of incompatibility with the media type specified on the request, the current data for the resource or the HTTP method specified on the request, test in a browser, usually there should be an indication of the problem.

ORA-29269: HTTP server error 500 -Internal Server Error -The target web server encountered an unexpected condition that prevented it from fulfilling the request by the client for access to the requested URL. This is an issue specific to the web server & cannot be resolved without intervention by the administrators of the target web server.  The Link Checker process will not handle all types of online media.