Lookup Oracle Error Codes From The Server

OERR

Oerr is an Oracle utility that extracts error messages with suggested actions from the standard Oracle message files. 
This utility is very useful as it can extract OS-specific errors that are not in the generic Error Messages and Codes Manual. 
Oerr is installed with the Oracle Database software and is located in the ORACLE_HOME/bin directory. 

Oracle doesn't ship an "oerr" utility for Windows platforms (a perl script is available to simulate oerr behaviour on Windows).

This is a shell script which works by finding the associated ORA message from a flat file in the rdbms dir.

You run the command from the server like this: 

oerr abc nnnnn  where oerr is the command, "abc" is the Oracle error code prefix (such as "ORA" for all Oracle error codes)  and the "nnnnn" represents the numeric portion of the Oracle error code (i.e. 01555).

So, for the famous snapshot to old error you would type:

oerr ORA 01555

This returns information about the possible cause of the issue as well as actions  required to resolve the issue.

/home/oracle $ oerr ORA 01555
01555, 00000, "snapshot too old: rollback segment number %s with name \"%s\" too small"
// *Cause: rollback records needed by a reader for consistent read are
//         overwritten by other writers
// *Action: If in Automatic Undo Management mode, increase undo_retention
//          setting. Otherwise, use larger rollback segments

This can be a useful tool and can be quicker than firing up a browser to search for details of the error code on-line.

Links:

Oracle FAQ - Oerr

Java World - Oracle Error Tool