SQL Gone Bad What to do when faulty SQL code corrupts your database Mary Louise Powers Tom Smull Lehigh University

Lehigh University technical environment All SCT Banner modules installed All Self Service products installed AIX/Unix, Oracle 9i Luminis / Portal

What can go wrong? Batch updates to the system An unnoticed semi-colon Fixes to the system People make mistakes

When it does go wrong Symptoms Scope (what / where / how many) Causes Possible Solutions / Resources Effect repairs Communicate / Document Punish Offenders

What tools are available? Most recent backup Last nights export LogMiner Flashback

LogMiner Allows DBA to examine contents of archived redo logs Especially: SQL_REDO, SQL_UNDO Knowing when the error occurred is helpful Knowing Oracle user who did it is also helpful

LogMiner script generation Need access to current data dictionary Which archive logs are to be searched? Which tables are suspect? Which user performed the erroneous update?

accept start_seq prompt 'Starting sequence: ' accept end_seq prompt ' Ending sequence: ' spool logminer_&start_seq select '-- exec dbms_logmnr_d.build(''ban6dictfile'',''/home/local/dba/logmnr'');' from sys.dual; select 'exec dbms_logmnr.add_logfile(LogFileName=>'''||name||''',Options=>dbms_logmnr.NEW);' from V_$ARCHIVED_LOG where SEQUENCE# = to_number('&start_seq'); select 'exec dbms_logmnr.add_logfile(LogFileName=>'''||name||''',Options=>dbms_logmnr.ADDFILE) ;' from V_$ARCHIVED_LOG where SEQUENCE# between (to_number('&start_seq') +1) and (to_number('&end_seq')) order by SEQUENCE#;

-- PART 2… select 'exec dbms_logmnr.start_logmnr(DictFileName=>''/~/dba/logmnr/ban6dictfile'');' from sys.dual; select 'spool LOGMNR.lst select to_char(timestamp,''YY-MM-DD HH24:MI:SS'') DATE_TIME, username, sql_redo /* your code goes here */ from sys.v_$logmnr_contents /* where seg_name IN (''SPBPERS''); */ spool off exec dbms_logmnr.end_logmnr;' from sys.dual; spool off

sys.v_$logmnr_contents (partial) Name Type SCN NUMBER CSCN NUMBER TIMESTAMP DATE COMMIT_TIMESTAMP DATE THREAD# NUMBER LOG_ID NUMBER. SEG_OWNER VARCHAR2(32) SEG_NAME VARCHAR2(256) SEG_TYPE_NAME VARCHAR2(32) ROW_ID VARCHAR2(19) SESSION# NUMBER SERIAL# NUMBER USERNAME VARCHAR2(30) OPERATION VARCHAR2(32) OPERATION_CODE NUMBER SQL_REDO VARCHAR2(4000) SQL_UNDO VARCHAR2(4000). SQL_COLUMN_TYPE VARCHAR2(32) SQL_COLUMN_NAME VARCHAR2(32)

-- exec dbms_logmnr_d.build('ban6dictfile','/home/local/dba/logmnr'); exec dbms_logmnr.add_logfile(LogFileName=>'/u5/ORACLE/arch_ban6_1_ dbf', Options=>dbms_logmnr.NEW); exec dbms_logmnr.add_logfile(LogFileName=>'/u5/ORACLE/arch_ban6_1_ dbf', Options=>dbms_logmnr.ADDFILE); exec dbms_logmnr.add_logfile(LogFileName=>'/u5/ORACLE/arch_ban6_1_ dbf', Options=>dbms_logmnr.ADDFILE); exec dbms_logmnr.add_logfile(LogFileName=>'/u5/ORACLE/arch_ban6_1_ dbf', Options=>dbms_logmnr.ADDFILE); exec dbms_logmnr.add_logfile(LogFileName=>'/u5/ORACLE/arch_ban6_1_ dbf', Options=>dbms_logmnr.ADDFILE); exec dbms_logmnr.start_logmnr(DictFileName=>'/home/local/dba/logmnr/ban6dictfile'); spool LOGMNR.lst select to_char(timestamp,'YY-MM-DD HH24:MI:SS') DATE_TIME, username, sql_redo, sql_undo from sys.v_$logmnr_contents where seg_name = 'SPBPERS'; and username = 'SATURN' spool off exec dbms_logmnr.end_logmnr;

-- FINAL GENERATED RECOVERY CODE: update "SATURN"."SPBPERS" set "SPBPERS_ETHN_CODE" = 'H' where "SPBPERS_ETHN_CODE" IS NULL and ROWID = 'AAAGIeAADAABX+KAA'; update "SATURN"."SPBPERS" set "SPBPERS_ETHN_CODE" = 'X' where "SPBPERS_ETHN_CODE" IS NULL and ROWID = 'AAAGIeAADAABX+KAA'; update "SATURN"."SPBPERS" set "SPBPERS_ETHN_CODE" = 'W' where "SPBPERS_ETHN_CODE" IS NULL and ROWID = 'AAAGIeAADAABX+KAA'; update "SATURN"."SPBPERS" set "SPBPERS_ETHN_CODE" = 'H' where "SPBPERS_ETHN_CODE" IS NULL and ROWID = 'AAAGIeAADAABX+KAB';

Oracle Flashback Lets you see data as it was in the past Allows online processing Need to know what was changed Can only go back as far as Undo Retention time Can restore accidental drop/delete Useful to reset tables in testing mode

Requirements/Limitations Oracle 9i or higher Must use Auto Undo Management Limited to undo retention time User must have certain privileges Flashback any/target table Execute on dbms_flashback

Flashback vs LogMiner Logminer lets you review transactions to see what happened. Flashback requires you to know what happened. Flashback is limited to the retention time – Logminer is limited by archivelog availability. Flashback can provide a before/after view of data in real time.

Flashback Query – Oracle9i Dbms_flashback package exec dbms_flashback.enable_at_time(…); select * from mytable; Exec dbms_flashback.disable;

declare Type pers_cursor is REF CURSOR; pcur pers_cursor; prow spbpers%ROWTYPE; BEGIN -- make sure no transactions or flashback in progress commit; dbms_flashback.disable; -- set the database back to previous time dbms_flashback.enable_at_time(to_timestamp ('16-NOV-2005', 'DD-MON-YY')); open pcur for 'select * from spbpers where spbpers_ethn_code is not null'; -- move back to present by disabling flashback. dbms_flashback.disable; LOOP fetch pcur into prow; exit when pcur%NOTFOUND; update spbpers set spbpers_ethn_code = prow.spbpers_ethn_code where spbpers_pidm = prow.spbpers_pidm and spbpers_ethn_code is null; commit; END LOOP; END;

Flashback Query – Oracle9i as of clause Select * from mytable as of timestamp …; Example : -- Restore rows erroneously deleted: insert into mytable (select * from mytable as of timestamp systimestamp - interval '15' minute minus select * from mytable);

Flashback Enhancements - 10g Flashback table Flashback database Version(s) query

Flashback Table Alternative to point in time recovery from backup. Restores table to earlier point in time or undrops table. Requires select, insert, delete, alter, and flashback privileges on table. To rewind table, enable row movement. Flashback table to timestamp. Recycle bin holds dropped tables.

Flashback table to earlier point in time alter table mytable enable row movement; flashback table mytable to SCN ; Or flashback table mytable to TIMESTAMP ;

Flashback Dropped Table FLASHBACK TABLE TO BEFORE DROP ORIGINAL NAME RECYCLEBIN NAME DROP TIME NAME_ADDR BIN$6u0c1Kv2wG7gM4C0PwLAbg==$ :19:25:47 NAME_ADDR BIN$6R5+rrqmwPbgM4C0PwLA9g==$ :19:30:19 MYTABLE BIN$BdpRTDoogGrgQ4C0PwKAag==$ :11:20:36 SQL> select * from "BIN$BdpRTDoogGrgQ4C0PwKAag==$0"; ID NAME Smull 2 Winwood 3 Smith SQL> flashback table "BIN$BdpRTDoogGrgQ4C0PwKAag==$0" to before drop; Flashback complete. SQL> select * from mytable; ID NAME Smull 2 Winwood 3 Smith

Managing These Tools Production vs Test Systems Audit Trails Templates

References Oracle Database Backup and Recovery Advanced User's Guide Oracle Database Backup and Recovery Basics Oracle Database Recovery Manager Reference

Questions?

Presenters Mary Louise Powers Tom Smull