Why are there multiple rows in V$SESSION_LONGOPS when running an RMAN backup?

Answer:
When performing an RMAN backup, V$SESSION_LONGOPS will be populated with two types of rows:

Detailed rows: Captures the progress of individual job steps.

Aggregated rows: Captures and summarizes the progress for the individual step of the backup job, as they complete. They are updated only after each detailed step has finished.

Example:
Below I am querying the V$SESSION_LONGOPS after an incremental backup level 0 has started, using 6 channels. Notice that there are both individual rows and an aggregated row present:

SELECT SID,SERIAL#,OPNAME,TARGET_DESC,TOTALWORK,SOFAR,UNITS,START_TIME,TIME_REMAINING,ELAPSED_SECONDS,MESSAGE
FROM V$SESSION_LONGOPS 
WHERE  TOTALWORK <> 0
AND SOFAR <> TOTALWORK
ORDER BY SERIAL# ASC;

SID	SERIAL#	OPNAME	TARGET_DESC	TOTALWORK	SOFAR	UNITS	START_TIME	TIME_REMAINING	ELAPSED_SECONDS	MESSAGE
203	7409	RMAN: incremental datafile backup	Set Count	4096000	1004926	Blocks	01.08.2014 12:28:28	557	181	RMAN: incremental datafile backup: Set Count 137085: 1004926 out of 4096000 Blocks done
398	15079	RMAN: incremental datafile backup	Set Count	3018368	1122302	Blocks	01.08.2014 12:28:28	306	181	RMAN: incremental datafile backup: Set Count 137088: 1122302 out of 3018368 Blocks done
439	17451	RMAN: incremental datafile backup	Set Count	2560000	1127038	Blocks	01.08.2014 12:28:29	229	180	RMAN: incremental datafile backup: Set Count 137089: 1127038 out of 2560000 Blocks done
357	31627	RMAN: incremental datafile backup	Set Count	3044608	1115518	Blocks	01.08.2014 12:28:28	313	181	RMAN: incremental datafile backup: Set Count 137087: 1115518 out of 3044608 Blocks done
476	55467	RMAN: incremental datafile backup	Set Count	2557440	940542	Blocks	01.08.2014 12:28:29	309	180	RMAN: incremental datafile backup: Set Count 137090: 940542 out of 2557440 Blocks done
512	55527	RMAN: aggregate input	backup	76514816	4360436	Blocks	01.08.2014 12:28:28	2085	126	RMAN: aggregate input: backup 33: 4360436 out of 76514816 Blocks done
281	56085	RMAN: incremental datafile backup	Set Count	3251200	969214	Blocks	01.08.2014 12:28:28	426	181	RMAN: incremental datafile backup: Set Count 137086: 969214 out of 3251200 Blocks done

Let's join V$SESSION_LONGOPS with V$SESSION and (if desirable) V$PROCESS, to view only the detailed rows, and estimate the progress in percent. This query is very useful to quickly get an overview of your backup, whether or not it is progressing according to expected speed etc:

SELECT S.CLIENT_INFO "Client Info", SL.OPNAME "Operation" ,SL.MESSAGE, SL.SID, SL.SERIAL#, P.SPID "OS Process ID", SL.SOFAR "So Far", SL.TOTALWORK "Totalwork", ROUND(SL.SOFAR/SL.TOTALWORK*100,2) "% complete"
FROM V$SESSION_LONGOPS SL INNER JOIN V$SESSION S ON SL.SID = S.SID 
                          INNER JOIN V$PROCESS P ON P.ADDR = S.PADDR
AND OPNAME LIKE 'RMAN%'
AND OPNAME NOT LIKE '%aggregate%'
AND TOTALWORK != 0
AND SOFAR <> TOTALWORK
/

Client Info	Operation	MESSAGE	SID	SERIAL#	OS Process ID	So Far	Totalwork	% complete
rman channel=tsm_channel_0	RMAN: incremental datafile backup	RMAN: incremental datafile backup: Set Count 137096: 1173118 out of 2252800 Blocks done	203	7409	42926864	1173118	2252800	52,07
rman channel=tsm_channel_1	RMAN: incremental datafile backup	RMAN: incremental datafile backup: Set Count 137095: 2029054 out of 2393600 Blocks done	281	56085	52101750	2029054	2393600	84,77
rman channel=tsm_channel_2	RMAN: incremental datafile backup	RMAN: incremental datafile backup: Set Count 137097: 293246 out of 2096640 Blocks done	357	31627	56361104	293246	2096640	13,99
rman channel=tsm_channel_3	RMAN: incremental datafile backup	RMAN: incremental datafile backup: Set Count 137099: 174206 out of 2048000 Blocks done	398	15079	52756692	174206	2048000	8,51
rman channel=tsm_channel_4	RMAN: incremental datafile backup	RMAN: incremental datafile backup: Set Count 137098: 460286 out of 2048000 Blocks done	439	17451	29032454	460286	2048000	22,47
rman channel=tsm_channel_5	RMAN: incremental datafile backup	RMAN: incremental datafile backup: Set Count 137100: 196094 out of 2048000 Blocks done	476	55467	9700724	196094	2048000	9,57

Notice how the V$RMAN_STATUS only hold information on aggregated level (2 rows, one for each operation although the first spawns the other):

SELECT SID,OPERATION,STATUS,MBYTES_PROCESSED, START_TIME, END_TIME, OBJECT_TYPE, OUTPUT_DEVICE_TYPE 
FROM V$RMAN_STATUS WHERE STATUS = 'RUNNING';

SID	OPERATION	STATUS	MBYTES_PROCESSED	START_TIME	OBJECT_TYPE	OUTPUT_DEVICE_TYPE
512	BACKUP	RUNNING	226641,953125	01.08.2014 12:28:28	DB INCR	SBT_TAPE
512	RMAN	RUNNING	0	01.08.2014 12:28:28

What is the difference between the columns PID and SPID in v$process?

The PID column is an internal counter that oracle uses for its own processes. It is incremented by one for every new process. Consequently, since every session creates its own server process (also called "shadow process") you will see the number increment by one for each session that connects.

The documentation for V$PROCESSES states that PID is the "Oracle Process Identifier" which is confusing.
In most circumstances, the column that you would need is the SPID, which shows the "Operating system process identifier".

More on the TO_DSINTERVAL conversion function

The TO_DSINTERVAL function is very flexible.
All you need to do is to specify the interval you're looking for, and it will convert your string into a valid INTERVAL datatype. Intervals are DAY, HOUR, MINUTE, SECOND

Examples:

Turn 2 days into a valid INTERVAL datatype

SELECT TO_DSINTERVAL(INTERVAL '2' DAY)
 FROM DUAL;

 TO_DSINTERVAL(INTERVAL'2'DAY)
 --------------------------------------------------
 +02 00:00:00.000000
 1 row selected.

Turn 75 minutes into a valid INTERVAL datatype

SELECT TO_DSINTERVAL(INTERVAL '75' MINUTE)
 FROM DUAL;

 TO_DSINTERVAL(INTERVAL'75'MINUTE)
 --------------------------------------------------
 +00 01:15:00.000000
 1 row selected.

Turn 60 minutes into a valid INTERVAL datatype

SELECT TO_DSINTERVAL(INTERVAL '60' MINUTE)
 FROM DUAL;

 TO_DSINTERVAL(INTERVAL'60'MINUTE)
 --------------------------------------------------
 +00 01:00:00.000000
 1 row selected.

Turn 60 seconds into a valid INTERVAL datatype

SELECT TO_DSINTERVAL(INTERVAL '60' SECOND)
 FROM DUAL;

 TO_DSINTERVAL(INTERVAL'60'SECOND)
 --------------------------------------------------
 +00 00:01:00.000000
 1 row selected.

Turn 24 hours into a valid INTERVAL datatype

SELECT TO_DSINTERVAL(INTERVAL '24' HOUR)
 FROM DUAL;

 TO_DSINTERVAL(INTERVAL'24'HOUR)
 --------------------------------------------------
 +01 00:00:00.000000
 1 row selected.

Turn 6 hours into a valid INTERVAL datatype

SELECT TO_DSINTERVAL(INTERVAL '6' HOUR)
 FROM DUAL;

 TO_DSINTERVAL(INTERVAL'6'HOUR)
 --------------------------------------------------
 +00 06:00:00.000000
 1 row selected.

Turn 61.2 seconds into a valid INTERVAL datatype

SELECT TO_DSINTERVAL(INTERVAL '61.2' SECOND)
 FROM DUAL;

 TO_DSINTERVAL(INTERVAL'61.2'SECOND)
 --------------------------------------------------
 +00 00:01:01.200000
 1 row selected.

Turn 1 hour into a valid INTERVAL datatype

SELECT TO_DSINTERVAL(INTERVAL '1' HOUR)
 FROM DUAL;

 TO_DSINTERVAL(INTERVAL'1'HOUR)
 --------------------------------------------------
 +00 01:00:00.000000
 1 row selected.

A convenient way to declare variables in PL/SQL

In PL/SQL programming, a convenient (and programmatically safe) way to specify data types for your variables is to let them be inherited from the table columns:

v_tab_name DBA_TABLES.TABLE_NAME%TYPE;
v_tabspc_name DBA_TABLES.TABLESPACE_NAME%TYPE;

How to drop stuck purge job created through DBMS_AUDIT_MGMT

In the process of implementing automatic purging of the audit trail, I came across a problem that I was really puzzled by: In the debugging process I had to drop and recreate the purge job that I had previously created through the dbms_audit_mgmt package.

I was completely unable to drop a particular scheduler job. All attempts threw different errors:

Trying to drop the job through the dbms_audit_mgmt.drop_purge_job procedure:

dbms_audit_mgmt.drop_purge_job(audit_trail_purge_name=>'PURGE_ALL_AUDIT_TRAILS');

Then trying to drop it directly through the dbms_scheduler.drop_job procedure:

dbms_scheduler.drop_job(job_name=>'PURGE_ALL_AUDIT_TRAILS',force=>TRUE);

Both attempts returned the error:

ERROR at line 1:
ORA-27475: "SYS.PURGE_ALL_AUDIT_TRAILS" must be a job
ORA-06512: at "SYS.DBMS_ISCHED", line 224
ORA-06512: at "SYS.DBMS_SCHEDULER", line 657
ORA-06512: at line 2

Trying to enable the job explicitly, in case the scheduled job was in an unknown state to the database:

exec dbms_scheduler.enable(name=>'PURGE_ALL_AUDIT_TRAILS');

which resulted in

ERROR at line 1:
ORA-27476: SYS.PURGE_ALL_AUDIT_TRAILS does not exist
ORA-06512: at "SYS.DBMS_ISCHED", line 4440
ORA-06512: at "SYS.DBMS_SCHEDULER", line 2803
ORA-06512: at line 1

Trying to recreate the job:

BEGIN
    DBMS_AUDIT_MGMT.create_purge_job(
      audit_trail_type           => DBMS_AUDIT_MGMT.AUDIT_TRAIL_ALL,
      audit_trail_purge_interval => 24 /* hours */,
      audit_trail_purge_name     => 'PURGE_ALL_AUDIT_TRAILS',
      use_last_arch_timestamp    => TRUE);
  EXCEPTION
    WHEN OTHERS THEN
     DBMS_OUTPUT.PUT_LINE(sqlerrm(sqlcode));
  END;
  /

Result:

ORA-46254: 'PURGE_ALL_AUDIT_TRAILS' already exists

Particuarly the last two error messages were discouraging. You cannot enable the job, because it doesn't exist, neither can you recreate the job, since it already DOES exist.

Solution:
From Oracle Support 1252235.1 "Unable to Create or Drop Purge Job Using DBMS_AUDIT_MGMT".

In short, log on as user sys and execute the following SQL statements:

SELECT JOB_NAME,STATE
FROM DBA_SCHEDULER_JOBS
WHERE JOB_NAME = 'PURGE_ALL_AUDIT_TRAILS'; <-- No rows should be returned

SELECT JOB_NAME,JOB_STATUS,AUDIT_TRAIL
FROM DBA_AUDIT_MGMT_CLEANUP_JOBS
WHERE JOB_NAME = 'PURGE_ALL_AUDIT_TRAILS'; <-- 1 row should be returned, the job that's "stuck"

DELETE FROM SYS.DAM_CLEANUP_JOBS$
WHERE JOB_NAME = 'PURGE_ALL_AUDIT_TRAILS'; <-- Delete the row from one of Oracle's internal tables,

COMMIT; <-- commit the change

And you're done, your job can be recreated, after which it will turn up as usual when you query the DBA_SCHEDULER_JOBS view:

SELECT STATE,ENABLED
FROM DBA_SCHEDULER_JOBS
WHERE  JOB_NAME = 'PURGE_ALL_AUDIT_TRAILS';

STATE	ENABLED
SCHEDULED	TRUE

How to purge the log entries for a specific dbms_scheduler job

exec dbms_scheduler.purge_log(log_history=>0, job_name=>'YOUR_JOB_NAME');

Zero is actually default for log_history, it doesn't have to be specified.

If you want to save some of the logs, you can specify for example that Oracle should only purge logs older than, say, two days:

exec dbms_scheduler.purge_log(log_history=>2, job_name=>'YOUR_JOB_NAME');

How to work around ORA-01830: date format picture ends before converting entire input string

When querying a column of type TIMESTAMP WITH TIMEZONE, I wanted to omit the fractional seconds + the time zone information.

The query

 SELECT STATE,
        START_DATE "START DATE"
 FROM   DBA_SCHEDULER_JOBS
 WHERE  OWNER = 'SYS' AND JOB_NAME = 'PURGE_ALL_AUDIT_TRAILS';

would return

STATE      START DATE
---------  --------------------------------
SCHEDULED  02.07.2014 13:351:16,558701 +02:00

and I simply didn't want to display that level of information. When trying to format the string as follows:

TO_DATE(START_DATE,'DD.MM.YYYY HH24:MI:SS') "START DATE"

I ran into the error:

   TO_DATE(START_DATE,'DD.MM.YYYY HH24:MI:SS') "START DATE"
                *
 ERROR at line 2:
 ORA-01830: date format picture ends before converting entire input string

Workaround:
In your session, set

ALTER SESSION SET NLS_TIMESTAMP_FORMAT='DD.MM.YYYY HH24:MI:SS';
ALTER SESSION SET NLS_DATE_FORMAT='DD.MM.YYYY HH24:MI:SS';

Then cast the data type from TIMESTAMP WITH TIMEZONE to TIMESTAMP:

CAST(START_DATE AS TIMESTAMP)

and finally, convert to DATE:

TO_DATE(CAST(START_DATE AS TIMESTAMP),'DD.MM.YYYY HH24:MI:SS')

Put together:

SELECT STATE,
        TO_DATE(CAST(START_DATE AS TIMESTAMP),'DD.MM.YYYY HH24:MI:SS') "START DATE"
 FROM   DBA_SCHEDULER_JOBS
 WHERE  OWNER = 'SYS' AND JOB_NAME = 'PURGE_ALL_AUDIT_TRAILS';

Output:

STATE           START DATE
 --------------- ------------------------------
 SCHEDULED       02.07.2014 13:51:16

Another example that worked for me was against a column defined like this:

  DATELASTUPDATED  TIMESTAMP(6)                 NOT NULL,

In my resultset I would only like dates from 29.12.2016, the time of the day is not interesting. Simply use the fuction TRUNC:

WHERE  trunc(DateLastUpdated) = '29.12.2016'