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Hypercharge SQL*Loader load speed performance

Oracle Tips by Burleson Consulting
February 2004, Updated February 22, 2008

Is there any limit to the speed of Oracle?  With Oracle announcing a new record one million transactions per minute, many believe that there is nothing that Oracle cannot do.  However, what if we have a requirement for a system that must accept high-volume data loads into a single table:

  • 500,000 rows per second
  • 50 megabytes per second

Is this possible? Using the right tricks you can make Oracle load data at unbelievable speed.  However, special knowledge and tricks are required.

Oracle provides us with many choices for online data loading: 

  • SQL insert and merge statements
  • PL/SQL bulk loads using the forall operator

If we can load in batch mode, we also have more options:

  • SQL*Loader
  • Oracle Data Pump
  • Oracle import utility

However there are vast differences in load speed (Figure 1).


Figure 1: Sample data load speeds

Batch Data Loading

If you are loading your data from flat files there are many products and Oracle tools to improve your load speed:

Oracle Data load tools:

    Oracle10g Data Pump - With Data Pump Import, a single stream of data load is about 15-45 times faster than original Import. This is because original Import uses only conventional mode inserts, whereas Data Pump Import uses the direct path method of loading.

    Oracle SQL*Loader - Oracle SQL*Loader has dozens of options including direct-path loads, unrecoverable, etc and get super-fast loads. Here are tips for getting high-speed loads with SQL*Loader.

    Oracle import Utility - Oracle has numerous options to improve data load speed with its import utility.

See my related notes on loading with SQL*Loader:

 
 
 
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Online Data Loading

Don't use standard SQL inserts as they are far slower than other approaches. If you must use SQL inserts, make sure to use the APPEND hint to bypass the freelists and raise the high-water mark for the table. You are way better off using PL/SQL with the bulk insert features (up to 100x faster).

Other things to ensure:

  • Use parallel DML - Parallelize the data loads according to the number of processors and disk layout. Try to saturate your processors with parallel processes. 
     

  • Disable constraints and indexes ? Disable RI during load and re-enable (in parallel) following the load.
     

  • Tune object parms - Use multiple freelists or freelist groups for target tables. Avoid using bitmap freelists ASS management (automatic segment space management) for super high-volume loads.
     

  • Pre-sort the data in index key order - This will make subsequent SQL run far faster for index range scans.
     

  • Use RAM Disk - Place undo tablespace and online redo logs on Solid-state disk (RAM SAN)
     

  • Use SAME RAID - Avoid RAID5 and use Oracle Stripe and Mirror Everywhere approach (RAID 0+1, RAID10). However, this doesn't mean one large array smeared with everything, you will see performance gains from separating temp, data and index, redo and undo segments onto separate RAID areas.
     

  • Use a small db_cache_size - This will minimize DBWR work. In Oracle9i you can use the alter system set db_cache_size command to temporarily reduce the data buffer cache size.
     

  • Watch your commit frequency - Too frequent checkpoints can be a performance issue. To few commits can cause undo segment problems.
     

  • Use a large blocksize - Data loads onto 32k blocksizes will run far faster because Oracle will be able to insert more rows into an empty block before a write.

    Here is a small benchmark showing the performance of loads into a larger blocksize:

    alter system set db_2k_cache_size=64m scope=spfile;
    alter system set db_16k_cache_size=64m scope=spfile;
    startup force
    create tablespace twok blocksize 2k; <-- using ASM defaults to 100m
    create tablespace sixteenk blocksize 16k;
    create table load2k tablespace twok as select * from dba_objects; < creates 8k rows
    drop table load2k; <- first create was to preload buffers

    set timing on;
    create table load2k tablespace twok as select * from dba_objects;
    create table load16k tablespace sixteenk as select * from dba_objects;


    For a larger sample, I re-issued the create processes with:

    select * from dba_source (80k rows).

    Even with this super-tiny sample on Linux using Oracle10g with ASM the results where impressive:

                                2k         16k
                              blksze      blksze
    8k table size            4.33 secs   4.16 secs
    80k table size           8.74 secs   8.31 secs

     

Driving your server

It is critical to take STATSPACK reports during data loading, paying special attention to the top-5 wait events.

    I/O-bound - Move to faster media (SSD), especially for undo and redo files.

    CPU-bound - Add more processors and increase degree of parallel DML

    Network-bound - Move data loading onto the save server as the Oracle instance

Using these techniques you can achieve blistering data load speeds for multi-terabyte Oracle databases.

If you like Oracle tuning, you might enjoy my book "Oracle Tuning: The Definitive Reference", with 950 pages of tuning tips and scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.


 

 

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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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