The Alert log file (also referred as Alert file) is a chronological log of messages and errors written out by an Oracle instance. Typical messages found in this file are: database startup, shutdown, log switches, space errors, etc. This file should be constantly monitored to detect unexpected messages and corruptions. The location of the alert file is known to Lab128, this information is queried from the monitored instance.
The Alert File Viewer window helps to examine the alert file by highlighting content, automatically detecting important events, and providing navigation means for locating these important events.
When the viewer is opened, it reads last N kilobytes of text from the alert file, and then incrementally appends new text as it becomes available. You can define how big the text buffer should be by changing value in the "Buffer Size, KB" edit box. This value should be between 30 and 10,000 KB (default is 500 KB). Once the buffer is filled up, it will become a moving window view on data in the alert file.
In order to read the alert file, Lab128 establishes secure shell (SSH) connection to the server, and then uses SFTP protocol. SFTP is supported by virtually all SSH implementations. You will be prompted to enter a user name / password and other attributes of an SSH (see SHH Login window) connection. If a connection is already opened by another window, it will be reused in this window.
This pane shows raw text from the alert file. For convenience, the timestamp of each entry is highlighted. Some other elements in the text are also highlighted, such as ORA- errors. References to other log files are shown as links in blue underlined text. Click on the link to see text of the file in a separate file viewer window.
The content of the alert file is analyzed automatically as it is loaded into the viewer. The important events are identified and put in a list shown in the Navigation pane. Each entry in the Navigation pane is first 23 characters of the text of the event in the alert file. Select a line in the navigation list, and corresponding entry in the alert file will be scrolled to and shown in the Viewer pane.
The entries in the Navigation pane don't include a timestamp to save space in its area. The entries are ordered by time and, for convenience, there are date separators placed between adjacent entries if they belong to different dates. Select the entry to see the full text in the viewer including the timestamp.
If the last entry in the viewer is visible, it will scroll down automatically as new data arrives. The "Go to End" button will scroll the text to the end and will put the viewer into auto-scroll mode. This mode is helpful when watching incoming events in real-time.