First i would thank CKPT for this amazing article that post in his blog .
Instead of reviewing whole alert log file for any Particular information, We can search using that key word from X$DBGALERTEXT Table.
Grep The word “Starting Up” of Alert log file from Instance.
col ORIGINATING_TIMESTAMP for a40
col MESSAGE_TEXT for a80
set linesize 500
SELECT
originating_timestamp,
message_text
FROM
sys.x$dbgalertext
WHERE
message_text LIKE '%Starting up%';
Grep The word “Instance shutdown complete” of Alert log file from Instance.
SELECT
originating_timestamp,
message_text
FROM
sys.x$dbgalertext
WHERE
message_text LIKE '%Instance shutdown complete%';
again thank you CKPT for this article since its useful for all DBA’s , you can check CKPT Blog From the above link
Thank you
Osama mustafa