Managing Alert Log Size in Oracle AI Database 26ai

By -

 Starting with Oracle AI Database 26ai (Release Update 23.9), it is possible to control the maximum size of the alert log using the ALERT_LOG_MAX_SIZE parameter. The default value for this parameter is 1000 MB, which means the XML alert log can grow up to a maximum of 20 segments, each 50 MB in size.

In my test, I configured the alert log maximum size to 100 MB:

SQL> ALTER SYSTEM SET alert_log_max_size = 100M;
System altered.

***This parameter is modifiable using ALTER SYSTEM, but it is not modifiable at the PDB level.

To increase the size of the alert log and force file generation, I executed the following PL/SQL block to continuously write messages into the alert log:

begin
  for i in 1 .. 1000000 loop
    begin
      sys.dbms_system.ksdwrt(2, 'Vahid Yousefzadeh');
    end;
  end loop;
end;
/

After running this block, there are several XML files in the alert directory and each file size is approximately 50MB.

[root@OEL9-DB2 alert]# ls -lh
-rw-r----- 1 oracle oinstall 51M Feb 23 11:57 log_20.xml
-rw-r----- 1 oracle oinstall 51M Feb 23 11:57 log_21.xml
-rw-r----- 1 oracle oinstall 16M Feb 23 11:57 log.xml

In addition, I checked the trace directory and observed multiple alert text log files:

[root@OEL9-DB2 trace]# ls -lh alert*.log
-rw-r----- 1 oracle oinstall 4.1M Feb 23 11:57 alert_db26ai_20.log
-rw-r----- 1 oracle oinstall 4.1M Feb 23 11:57 alert_db26ai_21.log
-rw-r----- 1 oracle oinstall 1.3M Feb 23 11:57 alert_db26ai.log

This behavior indicates that the size and number of alert text log files are driven by the XML log files.

Controlling XML Segment Size

There is also a hidden parameter called: _alert_segment_size

This parameter allows us to control the size of each XML alert log segment.

SQL> ALTER SYSTEM SET "_alert_segment_size" = 65;
System altered.

SQL> ALTER SYSTEM SET alert_log_max_size = 100M;
System altered.

After generating alert activity again, the results were:

Alert (XML) directory:

[root@OEL9-DB2 alert]# ll
-rw-r----- 1 oracle oinstall 68157489 Feb 23 12:05 log_25.xml
-rw-r----- 1 oracle oinstall 68157489 Feb 23 12:05 log_26.xml
-rw-r----- 1 oracle oinstall  2656020 Feb 23 12:05 log.xml

Trace directory:

[root@OEL9-DB2 trace]# ls -lh alert*.log
-rw-r----- 1 oracle oinstall 5.3M Feb 23 12:05 alert_db26ai_25.log
-rw-r----- 1 oracle oinstall 5.3M Feb 23 12:05 alert_db26ai_26.log
-rw-r----- 1 oracle oinstall 211K Feb 23 12:05 alert_db26ai.log

As shown above, each XML segment is now approximately 66 MB, which reflects the new _alert_segment_size value.

Disabling the Alert Log Size Limit

If we want to return to unlimited alert log growth, we can set the parameter to 0:

SQL> ALTER SYSTEM SET alert_log_max_size = 0;
System altered.

Vahid Yousefzadeh

Written by Vahid Yousefzadeh


I have been a DBA since 2011 and I work with Oracle technology. Linkdin: linkedin.com/in/vahidusefzadeh telegram channel ID:@oracledb vahidusefzadeh@gmail.com

Edit profile

Comments

Post a Comment

Popular posts from this blog

Oracle 21c Enhancements for TTS Export/Import

By -
  In Oracle version 21c, new features have been introduced for transportable tablespace (TTS) export/import. This article explores these capabilities in detail. Improvement 1: Parallel Execution of TTS Export/Import In Oracle 19c, TTS export/import operations could not be executed in parallel, as demonstrated by the following: Connected to: Oracle Database 19c Enterprise Edition Release 19.0 .0 .0 .0 – Production ORA-39002: invalid operation ORA-39047: Jobs of type TRANSPORTABLE cannot use multiple execution streams. Oracle addressed this limitation in version 21c, enabling parallel execution for TTS export/import: [oracle@oLinux7 ~]$ expdp directory=drm dumpfile=TTS_DUMP%U.dmp transport_tablespaces=tbs1,tbs2 transport_full_check= y parallel= 2 Export: Release 21.0 . 0 . 0 . 0 – Production on Tue Oct 12 06 : 48 : 54 2021 Version 21.3 . 0 . 0 . 0 Processing object type TRANSPORTABLE_EXPORT/STATISTICS/TABLE_STATISTICS Processing object type TRANSPORTABLE_EXPOR...
Read more

Oracle 23ai — Speed up IMPDP Using NOVALIDATE Constraints

By -
  When executing the   IMPDP   command, some operations do not support parallel execution. Creating constraints is one such operation. Oracle must validate the current data in the table before creating a constraint, which requires a full table scan for each validation. This process can be very time-consuming. Consider the following constraints: ALTER TABLE VAHID.MYTB ADD CONSTRAINT CHECK1 CHECK (col3 > 50 ); ALTER TABLE VAHID.MYTB ADD CONSTRAINT CHECK2 CHECK (col9 IN ( 5 , 15 )); We drop the  MYTB  table and recreate it using a dump file: SQL > drop table mytb; Table dropped. W -1 Processing object type TABLE_EXPORT / TABLE / TABLE_DATA W -1 . . imported "VAHID"."MYTB" 19 GB 337830912 rows in 83 seconds using external_table W -1 Processing object type TABLE_EXPORT / TABLE / CONSTRAINT / CONSTRAINT W -1 Completed 2 CONSTRAINT objects in 208 seconds As shown, creating the two constraints ta...
Read more

Staging Tables in Oracle 23ai

By -
  As you may know, using   staging tables   is a common practice in   Data Warehouse   environments, primarily during the data loading process into the   Warehouse Database . Typically, raw data received from   source databases   is first loaded into a temporary area, referred to as   staging tables . After cleansing inconsistent and invalid data and transforming it into a standard format, the cleaned data is stored in the final operational tables. In addition to initial data loading,   staging tables   are also used for updates and are often truncated before reuse. In   Oracle 23ai , a new minor feature has been introduced for this purpose, allowing users to create tables specifically designed as   staging tables . This is achieved by adding the   FOR STAGING   clause to the   CREATE TABLE   statement. Creating Staging Tables Using the   FOR STAGING   clause, staging tables can be created as ...
Read more