When setting, unsetting, or changing environment variables, a backup of the symbol.tbl file (symbol.bak) is maintained. If the original symbol.tbl file becomes corrupted, you can use the backup symbol table file to restore it. A history of updates to the symbol.tbl file is maintained in the symbol.log file. The symbol.bak and symbol.log files are located in the same location as the original symbol.tbl file. For more information, see the System Administrator Guide.