previous post<\/a> I traced the two purge method: purge all before a timestamp, or purge all. Here is the same in 12.2
\n<\/p>\nPurge old<\/h3>\n
I have quite a few record in Unified Audit Trail here.<\/p>\n
\nSQL> select unified_audit_policies,action_name,count(*) from unified_audit_trail group by unified_audit_policies,action_name;\n \nUNIFIED_AUDIT_POLICIES ACTION_NAME COUNT(*)\n---------------------------------------- -------------------- ----------\n EXECUTE 3\nORA_LOGON_FAILURES LOGON 408275\n<\/code><\/pre>\nI set the timestamp to 6 hours before now<\/p>\n
SQL> exec dbms_audit_mgmt.set_last_archive_timestamp(audit_trail_type=>dbms_audit_mgmt.audit_trail_unified\n,last_archive_time=>sysdate-6\/24);\nPL\/SQL procedure successfully completed.<\/code><\/pre>\nAnd call the clean procedure:<\/p>\n
SQL> exec dbms_audit_mgmt.clean_audit_trail(audit_trail_type=>dbms_audit_mgmt.audit_trail_unified\n,use_last_arch_timestamp=>TRUE);\nPL\/SQL procedure successfully completed.<\/code><\/pre>\nHere is what I see in the trace:<\/p>\n
select sys.dbms_audit_mgmt.is_droppable_partition(:1, :2)\nfrom\n dual<\/code><\/pre>\nThis is interesting. The Unified Audit Trail is partitioned on timestamp and the purge procedure checks it the partition can be dropped instead of running a long delete statement.<\/p>\n
Here is the documentation we have about it in ?\/rdbms\/admin\/dbmsamgt.sql<\/p>\n
-- is_droppable_partition - IS aud$unified table PARTITION DROPPABLE?\n --\n --\n -- INPUT PARAMETERS\n -- partname - aud$unified table's Partition Name\n -- lat - Last Archive Timestamp mentioned during cleanup\n<\/code><\/pre>\nIn my case, I traced the bind variables and the is_droppable_partition procedure was run only once with partname=>'”SYS_P348″‘ and lat=>’03-MAR-17 03.07.56 PM’. The timestamp is the ‘last timestamp’ I’ve set, and I have only one partition here because my database was created recently.<\/p>\n
As we can guess, this checks the high value of the partition:<\/p>\n
select high_value\nfrom\n dba_tab_partitions where table_owner = 'AUDSYS' and table_name =\n 'AUD$UNIFIED' and partition_name = :1<\/code><\/pre>\nBecause I have only one partition, which is the current one, my ‘last timestamp’ is below the high_value so it is not possible to truncate this partition and keep the records from after the ‘last timestamp’.<\/p>\n
Then a delete is run, which deletes all rows from before my last timestamp (bind variable :1 is ’03-MAR-17 03.07.56 PM’). Note that I don’t know (yet) why we can have DBID=0.<\/p>\n
delete from audsys.aud$unified\nwhere\n event_timestamp < :1 and (dbid = :2 or dbid = 0)\n \ncall count cpu elapsed disk query current rows\n------- ------ -------- ---------- ---------- ---------- ---------- ----------\nParse 1 0.00 0.00 0 0 0 0\nExecute 2 10.68 31.25 16885 24367 437518 346517\nFetch 0 0.00 0.00 0 0 0 0\n------- ------ -------- ---------- ---------- ---------- ---------- ----------\ntotal 3 10.68 31.25 16885 24367 437518 346517\n \nMisses in library cache during parse: 1\nMisses in library cache during execute: 1\nOptimizer mode: ALL_ROWS\nParsing user id: SYS (recursive depth: 1)\nNumber of plan statistics captured: 1\n \nRows (1st) Rows (avg) Rows (max) Row Source Operation\n---------- ---------- ---------- ---------------------------------------------------\n 0 0 0 DELETE AUD$UNIFIED (cr=12219 pr=16885 pw=0 time=31219023 us starts=1)\n 346517 346517 346517 PARTITION RANGE ITERATOR PARTITION: 1 KEY (cr=12148 pr=0 pw=0 time=1161311 us starts=1 cost=547 size=1231218 card=68401)\n 346517 346517 346517 TABLE ACCESS FULL AUD$UNIFIED PARTITION: 1 KEY (cr=12148 pr=0 pw=0 time=788043 us starts=1 cost=547 size=1231218 card=68401)\n \nElapsed times include waiting on following events:\n Event waited on Times Max. Wait Total Waited\n ---------------------------------------- Waited ---------- ------------\n PGA memory operation 5 0.00 0.00\n db file sequential read 16885 0.03 21.03\n<\/code><\/pre>\nAll my rows are deleted with conventional updates here. I had 400000 rows, deleted 340000 so 60000 remains.<\/p>\n
Purge old with old partitions<\/h3>\n
I had only one partition here but AUDSYS.AUD$UNIFIED is partitioned by month. Here is what I can see in my alert.log about the creation of this partition:<\/p>\n
TABLE AUDSYS.AUD$UNIFIED: ADDED INTERVAL PARTITION SYS_P348 (33) VALUES LESS THAN (TIMESTAMP' 2017-04-01 00:00:00')<\/code><\/pre>\nActually, this is automatically partitioned by months. Here is an excerpt of the table’s DDL as displayed by dbms_metadata:<\/p>\n
PARTITION BY RANGE (\"EVENT_TIMESTAMP\") INTERVAL (INTERVAL '1' MONTH)\n (PARTITION \"SYS_P348\" VALUES LESS THAN (TIMESTAMP' 2017-04-01 00:00:00') SEGMENT CREATION IMMEDIATE<\/code><\/pre>\nWhen running the same as before but on a database with few older partitions (because there were no scheduled purge) I can see that the ‘is_droppable_partition’ and the related query is run 4 times:<\/p>\n
select high_value\nfrom\n dba_tab_partitions where table_owner = 'AUDSYS' and table_name =\n 'AUD$UNIFIED' and partition_name = :1\n \ncall count cpu elapsed disk query current rows\n------- ------ -------- ---------- ---------- ---------- ---------- ----------\nParse 1 0.00 0.00 0 0 0 0\nExecute 4 0.05 0.05 0 0 0 0\nFetch 4 0.00 0.00 0 143 0 4\n------- ------ -------- ---------- ---------- ---------- ---------- ----------\ntotal 9 0.05 0.06 0 143 0 4<\/code><\/pre>\nand I see a drop partition for the 3 old partitions:<\/p>\n
ALTER TABLE AUDSYS.AUD$UNIFIED DROP PARTITION AUD_UNIFIED_P0\nALTER TABLE AUDSYS.AUD$UNIFIED DROP PARTITION SYS_P221\nALTER TABLE AUDSYS.AUD$UNIFIED DROP PARTITION SYS_P781<\/code><\/pre>\nNote that this is called by:<\/p>\n
CALL DBMS_PDB_EXEC_SQL('ALTER TABLE AUDSYS.AUD$UNIFIED DROP PARTITION SYS_P781')<\/code><\/pre>\nwhich runs it internally as an oracle script because this DDL is not allowed otherwise.<\/p>\n
In summary, purging with a timestamp is optimized to run conventional deletes only on latest partition. Older partitions are dropped. If you schedule a job to regularly set the timestamp and then have the purge job doing the cleaning, then better to set a timestamp at the beginning of the month. If you have to purge a large audit trail, then better to wait the beginning of the next month.<\/p>\n
Purge all<\/h3>\n
If you don’t need to keep recent records and want to truncate all, then just call the purge without timestamp.<\/p>\n
Here I have about 60000 rows remaining from the previous test, all in the current partition.<\/p>\n
SQL> select unified_audit_policies,action_name,count(*) from unified_audit_trail group by unified_audit_policies,action_name;\n \nUNIFIED_AUDIT_POLICIES ACTION_NAME COUNT(*)\n---------------------------------------- -------------------- ----------\n EXECUTE 6\nORA_LOGON_FAILURES LOGON 62152\n<\/code><\/pre>\nI call the clean<\/p>\n
SQL> exec dbms_audit_mgmt.clean_audit_trail(audit_trail_type=>dbms_audit_mgmt.audit_trail_unified\n,use_last_arch_timestamp=>FALSE);\nPL\/SQL procedure successfully completed.<\/code><\/pre>\nAnd I can see directly in the trace a truncate of the whole table:<\/p>\n
TRUNCATE TABLE AUDSYS.AUD$UNIFIED\n \ncall count cpu elapsed disk query current rows\n------- ------ -------- ---------- ---------- ---------- ---------- ----------\nParse 1 0.00 0.00 0 0 0 0\nExecute 1 0.04 4.42 67 6 919 0\nFetch 0 0.00 0.00 0 0 0 0\n------- ------ -------- ---------- ---------- ---------- ---------- ----------\ntotal 2 0.04 4.42 67 6 919 0\n \nMisses in library cache during parse: 1\nOptimizer mode: ALL_ROWS\nParsing user id: SYS (recursive depth: 1)\n \nElapsed times include waiting on following events:\n Event waited on Times Max. Wait Total Waited\n ---------------------------------------- Waited ---------- ------------\n db file sequential read 67 0.00 0.07\n enq: RO - fast object reuse 5 0.94 1.76\n local write wait 36 0.14 2.54<\/code><\/pre>\nThis is the fastest way to empty the Unified Audit Trail.<\/p>\n
So what?<\/h3>\n
We don’t have long experience on 12.2 production yet, but from what I see here, this new implementation is a good thing. There were many problems with the 12.1 implementations that are probably solved by having a normal table with normal interval partitioning, purged with normal deletes and normal truncates.
\nOf course, the next question is what happens when you upgrade a 12.1 database with a huge audit trail? That’s for a future post.
\nAnd don’t forget that by default you are in mixed mode. More info here<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"By Franck Pachot . A good thing from 12.2 is that the implementation of Unified Audit Trail has changed a little. It was stored in a weird CLI_SWP$ table but now we have a normal partitioned table named AUD$UNIFIED. In a previous post I traced the two purge method: purge all before a timestamp, or […]<\/p>\n","protected":false},"author":27,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[229],"tags":[656,1042,209],"type_dbi":[],"class_list":["post-9835","post","type-post","status-publish","format-standard","hentry","category-database-administration-monitoring","tag-12-2","tag-auditing","tag-oracle-12c"],"acf":[],"yoast_head":"\n
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