2 Replies Latest reply: Feb 1, 2013 10:48 AM by user8363520 RSS

    Backup: MML create a backup piece

    user8363520
      Hello all,

      I am on 11.2.0.3 DB(hpux ia64)....I had a question with regards to "Backup: MML create a backup piece"....from what i understand currently one of the session(1666) is waiting on my MML layer to start writing to tape...its waiting to create a backup piece...i totaly understand this is nothing to do with oracle being slow or anything(as its waiting on MML)...but my question is....have such long wait...would it effect my DB performance/server performance??

      I looked at the OEM page when my backup runs...while under the main performance page i do not see any graphs related to Administrative wait_class, its only when i look under the top activity page that i see graph that pops up the Administrative wait_class....is it bad that if this happens for a long time...is my server process in sleep state(but v$session shows active)...just wanted to understand a little more about "Backup: MML create a backup piece wait"....

      after even talking to the tape backup administrator we know we have some tape contention(as others backups are going on) this backup sits in the queue...some time it sits there for about 3-4 hours before it can start writing anything....
      SQL> SELECT   SID, event, total_waits, total_timeouts, time_waited, average_wait,
        2           max_wait, time_waited_micro/1000000
        3      FROM v$session_event
        4     WHERE SID = 1666
        5  ORDER BY SID, time_waited DESC
        6  ;
      
         SID|EVENT                                                           |TOTAL_WAITS|TOTAL_TIMEOUTS|TIME_WAITED|AVERAGE_WAIT|  MAX_WAIT|TIME_WAITED_MICRO/1000000
      ------|----------------------------------------------------------------|-----------|--------------|-----------|------------|----------|-------------------------
        1666|Backup: MML create a backup piece                               |          2|             0|      94974|    47487.05|     60510|               949.740924
        1666|Backup: MML write backup piece                                  |      82126|             0|      82815|        1.01|        28|               828.151483
        1666|RMAN backup & recovery I/O                                      |      36564|             0|      42769|        1.17|        28|               427.687802
        1666|Backup: MML commit backup piece                                 |          1|             0|        714|      714.16|       714|                 7.141612
        1666|SQL*Net message from client                                     |         73|             0|        658|        9.02|       319|                 6.582584
        1666|Backup: MML query backup piece                                  |          1|             0|        550|      550.02|       550|                 5.500196
        1666|events in waitclass Other                                       |        317|             2|        386|        1.22|        85|                 3.859556
        1666|control file sequential read                                    |        387|             0|         18|         .05|         1|                  .180209
        1666|Disk file operations I/O                                        |         71|             0|         13|         .18|         2|                  .125252
        1666|control file parallel write                                     |         21|             0|          6|         .26|         1|                  .055472
        1666|db file sequential read                                         |         27|             0|          3|         .11|         1|                  .029231
        1666|Backup: MML initialization                                      |          1|             0|          2|        1.57|         2|                  .015683
        1666|db file single write                                            |          9|             0|          1|         .09|         0|                  .007805
        1666|SQL*Net message to client                                       |         73|             0|          0|           0|         0|                  .000089
        1666|Backup: MML command to channel                                  |          1|             0|          0|         .01|         0|                  .000055
        1666|Backup: MML extended initialization                             |          1|             0|          0|           0|         0|                  .000003
      
      16 rows selected.
        • 1. Re: Backup: MML create a backup piece
          moreajays
          Hi,

          "Backup: MML create a backup piece" is related to backup media device waiting for TAPE allotment or to be picked up by drivers (you have also explained)
          Backup: MML create/write backup piece/RMAN backup & recovery I/O wait events are extending you db backup times which could have impact DB user IO.
          I have observed the same during DB Maintenance activities wherein a 2 GB shrink use to take hardly 30 minutes took an hour to complete when rman backup was in progress during night downtime windows
          Try disk to disk copy using SAN technologies & Take mirror disk/db backup on to TAPE to relieve direct IO overhead from production DB

          Refer below
          http://levipereira.wordpress.com/2012/08/09/what-is-slow-rman-or-media-management-library/

          Thanks,
          Ajay More
          http://www.moreajays.com
          • 2. Re: Backup: MML create a backup piece
            user8363520
            Thank you for the info. I had searched google before posting my question here and found the same link you posted here....

            I know what it dose(Backup: MML create a backup piece )...its waiting on MML...but my questions is dose it affect my DB performance/server performance...as my rman session is actively waiting on Backup: MML create a backup piece ....do my server process associated with it sleeps or spins on the cpu ??