How To Check Alert Log File in Oracle?

 Step 1: Connect to the database with SQL*Plus

===============================

[oracle@localhost ~]$ sqlplus / as sysdba

SQL*Plus: Release 19.0.0.0.0 - Production on Fri Apr 23 11:11:28 2021

Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup

ORACLE instance started.
Total System Global Area 1157627168 bytes
Fixed Size     8895776 bytes
Variable Size   436207616 bytes
Database Buffers   704643072 bytes
Redo Buffers     7880704 bytes
Database mounted.
Database opened.

Step 2: To view alert log, first you need to find it’s location using select command and exit the database

=========================================================================

SQL> select value from v$diag_info;

VALUE

--------------------------------------------------------------------------------

TRUE

/u01/app/oracle

/u01/app/oracle/diag/rdbms/orcl/orcl

/u01/app/oracle/diag/rdbms/orcl/orcl/trace

/u01/app/oracle/diag/rdbms/orcl/orcl/alert

/u01/app/oracle/diag/rdbms/orcl/orcl/incident

/u01/app/oracle/diag/rdbms/orcl/orcl/cdump

/u01/app/oracle/diag/rdbms/orcl/orcl/hm

/u01/app/oracle/diag/rdbms/orcl/orcl/trace/orcl_ora_4854.trc

0

0

VALUE

--------------------------------------------------------------------------------

/u01/app/oracle/product/19.3.0/dbhome_1

12 rows selected.

SQL> exit

Disconnected from Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production

Version 19.3.0.0.0

Step 3: In the V$DIAG_INFO query results, note the path that corresponds to the Diag Trace entry, and change directory to that path.

====================================================================== 

[oracle@localhost ~]$ cd /u01/app/oracle/diag/rdbms/orcl/orcl/trace

[oracle@localhost trace]$ ls -lrt

total 5656

-rw-r-----. 1 oracle oinstall    929 Apr 21 10:14 orcl_vktm_19514.trm

-rw-r-----. 1 oracle oinstall   1229 Apr 21 10:14 orcl_vktm_19514.trc

-rw-r-----. 1 oracle oinstall    926 Apr 21 10:14 orcl_ofsd_19529_19530.trm

-rw-r-----. 1 oracle oinstall   1061 Apr 21 10:14 orcl_ofsd_19529_19530.trc

-rw-r-----. 1 oracle oinstall   1982 Apr 21 10:17 orcl_ora_19711.trm

-rw-r-----. 1 oracle oinstall  20415 Apr 21 10:17 orcl_ora_19711.trc

-rw-r-----. 1 oracle oinstall   1892 Apr 21 10:17 orcl_ora_19784.trm

-rw-r-----. 1 oracle oinstall  11092 Apr 21 10:17 orcl_ora_19784.trc

-rw-r-----. 1 oracle oinstall    977 Apr 21 10:40 orcl_dia0_19747_base_1.trm

-rw-r-----. 1 oracle oinstall   4358 Apr 21 10:40 orcl_dia0_19747_base_1.trc

-rw-r-----. 1 oracle oinstall    866 Apr 21 10:40 orcl_ofsd_21949_21950.trm

-rw-r-----. 1 oracle oinstall    866 Apr 22 14:40 orcl_ofsd_12419_12420.trm

-rw-r-----. 1 oracle oinstall    993 Apr 22 14:40 orcl_ofsd_12419_12420.trc

-rw-r-----. 1 oracle oinstall   1211 Apr 22 14:43 orcl_lgwr_12434.trc

-rw-r-----. 1 oracle oinstall    887 Apr 22 14:43 orcl_tt02_12495.trm

-rw-r-----. 1 oracle oinstall  10980 Apr 22 14:44 orcl_ora_12481.trc

-rw-r-----. 1 oracle oinstall    866 Apr 22 14:44 orcl_ofsd_12875_12876.trm

-rw-r-----. 1 oracle oinstall    993 Apr 22 14:44 orcl_ofsd_12875_12876.trc

-rw-r-----. 1 oracle oinstall 337585 Apr 23 11:15 alert_orcl.log

-rw-r-----. 1 oracle oinstall    926 Apr 23 11:16 orcl_dbrm_4799.trm

-rw-r-----. 1 oracle oinstall   1640 Apr 23 11:16 orcl_dbrm_4799.trc

-rw-r-----. 1 oracle oinstall   2078 Apr 23 11:17 orcl_m003_5155.trc

-rw-r-----. 1 oracle oinstall    923 Apr 23 11:17 orcl_m001_5151.trm

-rw-r-----. 1 oracle oinstall    924 Apr 23 11:17 orcl_m002_5153.trm

-rw-r-----. 1 oracle oinstall   2008 Apr 23 11:17 orcl_m002_5153.trc

-rw-r-----. 1 oracle oinstall   2012 Apr 23 11:17 orcl_m001_5151.trc

Step 4: To view alert log you can use tail command with options and filename.

===========================================================

[oracle@localhost trace]$ tail -100f alert_orcl.log 

Patch Id: 29517242

Patch Description: Database Release Update : 19.3.0.0.190416 (29517242)

Patch Apply Time: 2019-04-18T12:51:17+05:30

Bugs Fixed: 14735102,19697993,20313356,21965541,25806201,25883179,25986062,

26476244,26611353,26872233,27369515,27423500,27666312,27710072,27846298,

27957203,28064977,28072567,28129791,28181021,28210681,28279456,28313275,

28350595,28371123,28379065,28431445,28463226,28489419,28502773,28513333,

28534475,28561704,28569897,28572533,28572544,28587723,28593682,28594086,

28597221,28601957,28605066,28606598,28625862,28627033,28636532,28643718,

28644549,28645570,28646200,28646939,28649388,28655209,28663782,28673945,

28692275,28694872,28696373,28705231,28710385,28710734,28714461,28718469,

28730079,28740708,28760206,28772390,28774416,28777214,28789531,28791852,

28795551,28802734,28804517,28810381,28811560,28815123,28815355,28819640,

28824482,28833912,28835937,28862532,28863432,28873575,28876253,28876639,

29462957,29486181,29507616,29515240,29521748,29530812,29531654,29557336,

29558975,29601461

Patch Id: 29585399

Patch Description: OCW RELEASE UPDATE 19.3.0.0.0 (29585399)

Patch Apply Time: 2019-04-18T12:51:33+05:30

Bugs Fixed: 3,27222128,27572040,27604329,27760043,27877830,28302580,28470673,

28621543,28642469,28699321,28710663,28755846,28772816,28785321,28800508,

28808652,28815557,28847541,28847572,28870496,28871040,28874416,28877252,

28881191,28881848,28888083,28911140,28925250,28925460,28935956,28940472,

28942694,28951332,28963036,28968779,28980448,28995287,29003207,29003617,

29016294,29018680,29024876,29026154,29027933,29047127,29052850,29058476,

29381000,29382296,29391301,29393649,29402110,29411931,29413360,29457319,

29465047

===========================================================

2021-04-23T11:15:35.193021+05:30

db_recovery_file_dest_size of 8256 MB is 43.81% used. This is a

user-specified limit on the amount of space that will be used by this

database for recovery-related files, and does not reflect the amount of

space available in the underlying filesystem or ASM diskgroup.