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Gather Statistics with DBMS_STATS by Jeff

February 20th, 2009 Leave a comment Go to comments


Contents

  1. Overview
  2. Missing statistics
  3. Analyze vs. DBMS_STATS
  4. What gets collected?
  5. Where are the statistics stored?
  6. Compute statistics vs. Estimate statistics
  7. DBMS_STATS functions and variable definitions
  8. DBMS_STATS in action (Examples)
  9. Automated table monitoring and stale statistics gathering example
  10. How to determine if dictionary statistics are RDBMS-generated or user-defined

Overview

Oracle’s cost-based optimizer (COB) uses statistics to calculate the selectivity (the fraction of rows in a table that the SQL statement’s predicate chooses) of predicates and to estimate the “cost” of each execution plan. The COB will use the selectivity of a predicate to estimate the cost of a particular access method and to determin the optimal join order. Statistics are used to quantify the data distribution and storage characteristics of tables, columns, indexes and partitions. The COB uses these statistics to estimate how much I/O and memory are required to execute a SQL statement using a particular execution plan. Statistics are stored in the data dictionary, and they can be exported from one database and imported into another. Situations in where you would want to perform this, might be to transfer production statistics to a test system to simulate the real environment, even though the test system may only have small samples of the data.

In order to give the Oracle cost-based optimizer the most up-to-date information about schema objects (and the best chance for choosing a good execution plan) all application tables and indexes to be accessed must be analyzed. New statistics should be gathered on schema objects that are out of date. After loading or deleting large amounts of data would obviously change the number of rows. Other changes like updating a large amount of rows would not effect the number of rows, but may effect the average row length.

Statistics can be generated with the ANALYZE statement or with the package DBMS_STATS (introduced in Oracle8i). The DBMS_STATS package is great for DBA’s in managing database statistics only for use by the COB. The package itself allows the DBA to create, modify, view and delete statistics from a standard, well-defined set of package procedures. The statistics can be gathered on tables, indexes, columns, partitions and schemas, but note that it does not generate statistics for clusters.

DBMS_STATS provides a mechanism for you to view and modify optimizer statistics gathered for database objects.The statistics can reside in two different locations:

Only statistics stored in the dictionary itself have an impact on the cost-based optimizer.

When you generate statistics for a table, column, or index, if the data dictionary already contains statistics for the object, then Oracle updates the existing statistics. Oracle also invalidates any currently parsed SQL statements that access the object.

The next time such a statement executes, the optimizer automatically chooses a new execution plan based on the new statistics. Distributed statements issued on remote databases that access the analyzed objects use the new statistics the next time Oracle parses them.

When you associate a statistics type with a column or domain index, Oracle calls the statistics collection method in the statistics type if you analyze the column or domain index.

Missing statistics

When statistics do not exist on schema objects, the optimizer uses the following default values.

Tables
Statistic Default Value Used by Optimizer
Cardinality 100 rows
Avg. row len 20 bytes
No. of blocks 100
Remote cardinality 2000 rows
Remote average row length 100 bytes
Indexes
Statistic Default Value Used by Optimizer
Levels 1
Leaf blocks 25
Leaf blocks/key 1
Data blocks/key 1
Distinct keys 100
Clustering factor 800 (8*no. of blocks)

Analyze vs. DBMS_STATS

The following is a quick overview of the two.

What gets collected?

Table Statistics

Oracle collects the following statistics for a table. Statistics marked with an asterisk are always computed exactly. Table statistics, including the status of domain indexes, appear in the data dictionary views USER_TABLES, ALL_TABLES, and DBA_TABLES in the columns shown in parentheses.

Index Statistics

Oracle collects the following statistics for an index. Statistics marked with an asterisk are always computed exactly. For conventional indexes, the statistics appear in the data dictionary views USER_INDEXES, ALL_INDEXES, and DBA_INDEXES in the columns in parentheses.

Where are the statistics stored?

Statistics are stored into the Oracle Data Dictionary, in tables owned by SYS. Views are created on these tables to retrieve data more easily. These views are prefixed with DBA_ or ALL_ or USER_. For ease of reading, we will use DBA_% views, but ALL_% views or USER_% views could be used as well.

Conventions Used 

- Statistics available only since 8.0.X rdbms release         : (*)
- Statistics available only since 8.1.X rdbms release         : (**)
- Statistics not available at partition or subpartition level : (G)
- Statistics not available at subpartition level              : (GP)

Table level statistics can be retrieved from:

  • DBA_ALL_TABLES – (8.X onwards)
  • DBA_OBJECT_TABLES – (8.X onwards
  • DBA_TABLES – (all versions)
  • DBA_TAB_PARTITIONS – (8.X onwards)
  • DBA_TAB_SUBPARTITIONS – (8.1 onwards) Columns to look at are: 
      NUM_ROWS                         : Number of rows (always exact even when computed
                                     with ESTIMATE method)
  BLOCKS                           : Number of blocks which have been used even
                                     if they are empty due to delete statements
  EMPTY_BLOCKS                     : Number of empty blocks (these blocks have
                                     never been used)
  AVG_SPACE                        : Average amount of FREE space in bytes in blocks
                                     allocated to the table : Blocks + Empty Blocks
  CHAIN_CNT                        : Number of chained or migrated rows
  AVG_ROW_LEN                      : Average length of rows in bytes
  AVG_SPACE_FREELIST_BLOCKS (*)(G) : Average free space of blocks in the freelist
  NUM_FREELIST_BLOCKS       (*)(G) : Number of blocks in the freelist
  SAMPLE_SIZE                      : Sample defined in ESTIMATE method (0 if COMPUTE)
  LAST_ANALYZED                    : Timestamp of last analysis
  GLOBAL_STATS             (**)    : For partitioned tables, YES means statistics
                                     are collected for the TABLE as a whole
                                     NO means statistics are estimated from statistics
                                     on underlying table partitions or subpartitions 
  USER_STATS               (**)    : YES if statistics entered directly by the user

    • Index level statistics can be retrieved from:

  • DBA_INDEXES – (all versions )
  • DBA_IND_PARTITIONS – (8.X onwards)
  • DBA_IND_SUBPARTITIONS – (8.1 onwards ) Columns to look at are: 
      BLEVEL                       : B*Tree level : depth of the index from its root
                                 block to its leaf blocks
  LEAF_BLOCKS                  : Number of leaf blocks
  DISTINCT_KEYS                : Number of distinct keys
  AVG_LEAF_BLOCKS_PER_KEY      : Average number of leaf blocks in which each
                                 distinct key appears (1 for a UNIQUE index)
  AVG_DATA_BLOCKS_PER_KEY      : Average number of data blocks in the table that
                                 are pointed to by a distinct key
  CLUSTERING_FACTOR            : - if near the number of blocks, then the table is
                                   ordered : index entries in a single leaf block
                                   tend to point to rows in same data block
                                 - if near the number of rows, the table is
                                   randomly ordered : index entries in a single
                                   leaf block are unlikely to point to rows in
                                   same data block
  SAMPLE_SIZE                  : Sample defined in ESTIMATE method (0 if COMPUTE)
  LAST_ANALYZED                : Timestamp of last analysis
  GLOBAL_STATS            (**) : For partitioned indexes, YES means statistics
                                 are collected for the INDEX as a whole
                                 NO means statistics are estimated from statistics
                                 on underlying index partitions or subpartitions
  USER_STATS              (**) : YES if statistics entered directly by the user
  PCT_DIRECT_ACCESS   (**)(GP) : For secondary indexes on IOTs, percentage of
                                 rows with VALID guess

    • Column level statistics can be retrieved from:

  • DBA_TAB_COLUMNS – (all versions)
  • DBA_TAB_COL_STATISTICS – (Version 8.X onwards)
  • DBA_PART_COL_STATISTICS – (Version 8.X onwards)
  • DBA_SUBPART_COL_STATISTICS – (Version 8.1 onwards) The last three views extract statistics data from DBA_TAB_COLUMNS. Columns to look at are: 
      NUM_DISTINCT                 : Number of distinct values
  LOW_VALUE                    : Lowest value
  LOW_VALUE                    : Highest value
  DENSITY                      : Density
  NUM_NULLS                    : Number of columns having a NULL value
  AVG_COL_LEN                  : Average length in bytes
  NUM_BUCKETS                  : Number of buckets in histogram for the column
  SAMPLE_SIZE                  : Sample defined in ESTIMATE method (0 if COMPUTE)
  LAST_ANALYZED                : Timestamp of last analysis
  (**)GLOBAL_STATS             : For partitioned tables, YES means statistics
                                 are collected for the TABLE as a whole
                                 NO means statistics are estimated from statistics
                                 on underlying table partitions or subpartitions
  (**)USER_STATS               : YES if statistics entered directly by the user

    • Compute statistics vs. Estimate statistics

    Both computed and estimated statistics are used by the Oracle optimizer to choose the execution plan for SQL statements that access analyzed objects. These statistics may also be useful to application developers who write such statements. COMPUTE STATISTICS

    COMPUTE STATISTICS instructs Oracle to compute exact statistics about the analyzed object and store them in the data dictionary. When computing statistics, an entire object is scanned to gather data about the object. This data is used by Oracle to compute exact statistics about the object. Slight variances throughout the object are accounted for in these computed statistics. Because an entire object is scanned to gather information for computed statistics, the larger the size of an object, the more work that is required to gather the necessary information.

    To perform an exact computation, Oracle requires enough space to perform a scan and sort of the table. If there is not enough space in memory, then temporary space may be required. For estimations, Oracle requires enough space to perform a scan and sort of only the rows in the requested sample of the table. For indexes, computation does not take up as much time or space, so it is best to perform a full computation.

    Some statistics are always computed exactly, such as the number of data blocks currently containing data in a table or the depth of an index from its root block to its leaf blocks. 某些信息总被精确地统计，如表当前使用的block数、index的高度

    Use estimation for tables and clusters rather than computation, unless you need exact values. Because estimation rarely sorts, it is often much faster than computation, especially for large tables.

    ESTIMATE STATISTICS

    ESTIMATE STATISTICS instructs Oracle to estimate statistics about the analyzed object and stores them in the data dictionary. When estimating statistics, Oracle gathers representative information from portions of an object. This subset of information provides reasonable, estimated statistics about the object. The accuracy of estimated statistics depends upon how representative the sampling used by Oracle is. Only parts of an object are scanned to gather information for estimated statistics, so an object can be analyzed quickly. You can optionally specify the number or percentage of rows that Oracle should use in making the estimate.

    To estimate statistics, Oracle selects a random sample of data. You can specify the sampling percentage and whether sampling should be based on rows or blocks.

    estimate statistics会随机选择样本大小。你可以定义基于row数或block数样本的大小

    Notes on estimating statistics

    DBMS_STATS functions and variable definitions

    Most of the DBMS_STATS procedures include the three parameters statown, stattab, and statid. These parameters allow you to store statistics in your own tables (outside of the dictionary), which does not affect the optimizer. Therefore, you can maintain and experiment with sets of statistics. The stattab parameter specifies the name of a table in which to hold statistics, and it is assumed that it resides in the same schema as the object for which statistics are collected (unless the statown parameter is specified). Users may create multiple tables with different stattab identifiers to hold separate sets of statistics.

    Additionally, users can maintain different sets of statistics within a single stattab by using the statid parameter, which can help avoid cluttering the user’s schema.

    For all of the SET or GET procedures, if stattab is not provided (i.e., NULL), then the operation works directly on the dictionary statistics; therefore, users do not need to create these statistics tables if they only plan to modify the dictionary directly. However, if stattab is not NULL, then the SET or GET operation works on the specified user statistics table, and not the dictionary.

    Create Stats Table 

    DBMS_STATS.CREATE_STAT_TABLE (
  ownname  VARCHAR2,
  stattab  VARCHAR2,
  tblspace VARCHAR2 DEFAULT NULL);

    Drop Stats Table 

    DBMS_STATS.drop_stat_table (
  ownname VARCHAR2,
  stattab VARCHAR2);

    Gather Schema Stats 

    DBMS_STATS.gather_schema_stats (
  ownname          VARCHAR2,
  estimate_percent NUMBER   DEFAULT NULL,
  block_sample     BOOLEAN  DEFAULT FALSE,
  method_opt       VARCHAR2 DEFAULT 'FOR ALL COLUMNS SIZE 1',
  degree           NUMBER   DEFAULT NULL,
  granularity      VARCHAR2 DEFAULT 'DEFAULT',
  cascade          BOOLEAN  DEFAULT FALSE,
  stattab          VARCHAR2 DEFAULT NULL,
  statid           VARCHAR2 DEFAULT NULL,
  options          VARCHAR2 DEFAULT 'GATHER',
  objlist     OUT  ObjectTab,
  statown          VARCHAR2 DEFAULT NULL);

    Export Schema Stats 

    DBMS_STATS.export_schema_stats (
  ownname VARCHAR2,
  stattab VARCHAR2,
  statid  VARCHAR2 DEFAULT NULL,
  statown VARCHAR2 DEFAULT NULL);

    Import Schema Stats 

    DBMS_STATS.import_schema_stats (
  ownname VARCHAR2,
  stattab VARCHAR2,
  statid  VARCHAR2 DEFAULT NULL,
  statown VARCHAR2 DEFAULT NULL);

    Delete Schema Stats 

    DBMS_STATS.delete_schema_stats (
  ownname VARCHAR2,
  stattab VARCHAR2 DEFAULT NULL,
  statid  VARCHAR2 DEFAULT NULL,
  statown VARCHAR2 DEFAULT NULL);

    Set Table Stats 手工设置统计信息

    DBMS_STATS.set_table_stats (
  ownname  VARCHAR2,
  tabname  VARCHAR2,
  partname VARCHAR2 DEFAULT NULL,
  stattab  VARCHAR2 DEFAULT NULL,
  statid   VARCHAR2 DEFAULT NULL,
  numrows  NUMBER   DEFAULT NULL,
  numblks  NUMBER   DEFAULT NULL,
  avgrlen  NUMBER   DEFAULT NULL,
  flags    NUMBER   DEFAULT NULL,
  statown  VARCHAR2 DEFAULT NULL);

    Get Table Stats 

    DBMS_STATS.get_table_stats (
  ownname     VARCHAR2,
  tabname     VARCHAR2,
  partname    VARCHAR2 DEFAULT NULL,
  stattab     VARCHAR2 DEFAULT NULL,
  statid      VARCHAR2 DEFAULT NULL,
  numrows OUT NUMBER,
  numblks OUT NUMBER,
  avgrlen OUT NUMBER,
  statown     VARCHAR2 DEFAULT NULL);

    Get Index Stats 

    DBMS_STATS.GET_INDEX_STATS (
  ownname      VARCHAR2,
  indname      VARCHAR2,
  partname     VARCHAR2 DEFAULT NULL,
  stattab      VARCHAR2 DEFAULT NULL,
  statid       VARCHAR2 DEFAULT NULL,
  numrows  OUT NUMBER,
  numlblks OUT NUMBER,
  numdist  OUT NUMBER,
  avglblk  OUT NUMBER,
  avgdblk  OUT NUMBER,
  clstfct  OUT NUMBER,
  indlevel OUT NUMBER,
  statown      VARCHAR2 DEFAULT NULL);

    DBMS_STATS in action (Examples)

    Create Stats Table 

    BEGIN
  DBMS_STATS.create_stat_table (
    ownname  => 'scott',
    stattab  => 'stats_table',
    tblspace => 'users');
END;
/

    Drop Stats Table 

    BEGIN
  DBMS_STATS.drop_stat_table (
    ownname => 'scott',
    stattab => 'stats_table');
END;
/

    Gather Schema Stats to Data Dictionary 

    BEGIN
  DBMS_STATS.gather_schema_stats (
    ownname          => 'scott',
    estimate_percent => null,
    block_sample     => false,
    method_opt       => 'FOR ALL COLUMNS SIZE 1',
    degree           => null,
    granularity      => 'ALL',
    cascade          => true,
    options          => 'GATHER');
END;
/

    Gather Schema Stats to Stats Table 

    BEGIN
  DBMS_STATS.gather_schema_stats (
    ownname          => 'scott',
    estimate_percent => null,
    block_sample     => false,
    method_opt       => 'FOR ALL COLUMNS SIZE 1',
    degree           => null,
    granularity      => 'ALL',
    cascade          => true,
    stattab          => 'stats_table',
    statid           => 'TEST1',
    options          => 'GATHER',
    statown          => 'scott');
END;
/

    Export Schema Statistics from Data Dictionary to Stats Table 

    BEGIN
  DBMS_STATS.export_schema_stats (
    ownname  => 'scott',
    stattab  => 'stats_table_backup',
    statid   => 'BACKUP_TEST1',
    statown  => 'scott');
END;
/

    Import Schema Statistics from Data Dictionary to Stats Table 

    BEGIN
  DBMS_STATS.import_schema_stats (
    ownname  => 'scott',
    stattab  => 'stats_table',
    statid   => 'TEST1',
    statown  => 'scott');
END;
/

    Delete Schema Stats from Data Dictionary 

    BEGIN
  DBMS_STATS.delete_schema_stats ('scott');
END;
/

    Delete Schema Stats from Stats Table 

    BEGIN
  DBMS_STATS.delete_schema_stats (
    ownname  => 'scott',
    stattab  => 'stats_table_backup',
    statid   => 'BACKUP_TEST1',
    statown  => 'scott');
END;
/

    Set Table Stats (Manually) in the Data Dictionary 

    BEGIN
  DBMS_STATS.set_table_stats (
    ownname  => 'scott',
    tabname  => 'emp',
    partname => null,
    numrows  => 650000000,
    numblks  => 53455443,
    avgrlen  => 212,
    flags    => null);
END;
/

    Set Table Stats (Manually) in the Stats Table 

    BEGIN
  DBMS_STATS.set_table_stats (
    ownname  => 'scott',
    tabname  => 'emp',
    partname => null,
    stattab  => 'stats_table',
    statid   => 'TEST1',
    numrows  => 650000000,
    numblks  => 53455443,
    avgrlen  => 212,
    flags    => null,
    statown  => 'scott');
END;
/

    Get Table Statistics in SQL*Plus Variables 

    SQL> variable NUMROWS number
SQL> variable NUMBLKS number
SQL> variable AVGRLEN number

BEGIN
  DBMS_STATS.get_table_stats (
    'scott',
    'emp',
    NUMROWS=>:numrows,
    NUMBLKS=>:numblks,
    AVGRLEN=>:avgrlen);
END;
/

PL/SQL procedure successfully completed.

SQL> print NUMROWS NUMBLKS AVGRLEN

   NUMROWS
----------
      1000

   NUMBLKS
----------
        28

   AVGRLEN
----------
        92

    Get Index Statistics in SQL*Plus Variables 

    SQL> variable NUMROWS number
SQL> variable NUMLBLKS number
SQL> variable NUMDIST number
SQL> variable AVGLBLK number
SQL> variable AVGDBLK number
SQL> variable CLSTFCT number
SQL> variable INDLEVEL number

BEGIN
  DBMS_STATS.get_index_stats (
    'SCOTT',
    'EMP_PK',
    NUMROWS   => :NUMROWS,
    NUMLBLKS  => :NUMLBLKS,
    NUMDIST   => :NUMDIST,
    AVGLBLK   => :AVGLBLK,
    AVGDBLK   => :AVGDBLK,
    CLSTFCT   => :CLSTFCT,
    INDLEVEL  => :INDLEVEL);
 END;
/

PL/SQL procedure successfully completed.

SQL> print NUMROWS NUMLBLKS NUMDIST AVGLBLK AVGDBLK CLSTFCT INDLEVEL

   NUMROWS
----------
      1000

  NUMLBLKS
----------
         3

   NUMDIST
----------
      1000

   AVGLBLK
----------
         1

   AVGDBLK
----------
         1

   CLSTFCT
----------
        15

  INDLEVEL
----------
         1

    Automated table monitoring and stale statistics gathering example

    You can automatically gather statistics or create lists of tables that have stale or no statistics.

    To automatically gather statistics, run the DBMS_STATS.GATHER_SCHEMA_STATS and DBMS_STATS.GATHER_DATABASE_STATS procedures with the OPTIONS and objlist parameters. Use the following values for the options parameter:

    The objlist parameter identifies an output parameter for the LIST STALE and LIST EMPTY options. The objlist parameter is of type DBMS_STATS.OBJECTTAB.

    Step 1 : Perform a quick analyze to load in base statistics 

    BEGIN
DBMS_STATS.GATHER_SCHEMA_STATS (
  ownname           => 'scott',
  estimate_percent  => null,              -- Small table, lets compute
  block_sample      => false,
  method_opt        => 'FOR ALL COLUMNS',
  degree            => null,              -- No parallelism used in this example
  granularity       => 'ALL',
  cascade           => true,              -- Make sure we include indexes
  options           => 'GATHER'           -- Gather mode
  );
END;
/

PL/SQL procedure successfully completed.

    Step 2 : Examine the current statistics 

    SELECT table_name, num_rows, blocks, avg_row_len
FROM user_tables
WHERE table_name='EMP';

TABLE_NAME                       NUM_ROWS     BLOCKS AVG_ROW_LEN
------------------------------ ---------- ---------- -----------
EMP                                  1500         28          92

    Step 3 : Turn on Automatic Monitoring

    Now turn on automatic monitoring for the emp table. This can be done using the alter table method. Starting with Oracle 9i, you can also perform this at the “schema”, and “entire database” level. I provide the syntax for all three methods below. Monitor only the EMP table. 

    alter table emp monitoring;

Table altered.

    Monitor all of the tables within Scott’s schema. (Oracle 9i and higher) 

    BEGIN
  DBMS_STATS.alter_schema_tab_monitoring('scott', true);
END;
/

PL/SQL procedure successfully completed.

    Monitor all of the tables within the database. (Oracle 9i and higher) Note: Although the option to collect statistics for SYS tables is available via ALTER_DATABASE_TAB_MONITORING, Oracle continues to recommend against this practice until the next major release after 9i Release 2. Also note that the ALTER_DATABASE_TAB_MONITORING procedure in the DBMS_STATS package only monitors tables; there is an ALTER INDEX…MONITORING statement which can be used to monitor indexes. Thanks to Nabil Nawaz for providing this and pointing out an error I made in the previous version of this article. 

    BEGIN
  DBMS_STATS.alter_database_tab_monitoring (
    monitoring => true,
    sysobjs    => false);      -- Don't set to true, see note above.
END;
/

PL/SQL procedure successfully completed.

    Step 4 : Verify that monitoring is turned on.

    Note: The results of the following query are from running the alter table ... statement on the emp table only. 

    SELECT table_name, monitoring
FROM user_tables
ORDER BY monitoring;

TABLE_NAME                     MONITORING
------------------------------ ----------
DEPT                           NO
EMP                            YES

    Step 5 : Delete some rows from the database. 

    SQL> DELETE FROM emp WHERE rownum < 501;

500 rows deleted.

SQL> commit;

Commit complete.

    Step 6 : Wait until the monitered data is flushed.

    Data can be flushed in several ways.

    OK, I’m impatient… 

    exec dbms_stats.flush_database_monitoring_info;

PL/SQL procedure successfully completed.

    Step 7 : Check for what it has collected.

    As user “scott”, check USER_TAB_MODIFICATIONS to see what it was collected. 

    SELECT * FROM user_tab_modifications;

TABLE_NAME PARTITION_NAME SUBPARTITION_NAME INSERTS UPDATES DELETES TIMESTAMP TRUNCATED
---------- -------------- ----------------- ------- ------- ------- --------- ---------
EMP                                               0       0     500 18-SEP-02 NO

    Step 8 : Execute DBMS_STATS to gather stats on all “stale” tables. 

    BEGIN
  DBMS_STATS.GATHER_SCHEMA_STATS(
    ownname           => 'scott',
    estimate_percent  => null,
    block_sample      => false,
    method_opt        => 'FOR ALL COLUMNS',
    degree            => null,
    granularity       => 'ALL',
    cascade           => true,
    options           => 'GATHER STALE');
END;
/

PL/SQL procedure successfully completed.

    Step 9 : Verify that the table is no longer listed in USER_TAB_MODIFICATIONS. 

    SQL> SELECT * FROM user_tab_modifications;

no rows selected.

    Step 10 : Examine some of new statistics collected. 

    SELECT table_name, num_rows, blocks, avg_row_len
FROM user_tables where table_name='EMP';

TABLE_NAME                       NUM_ROWS     BLOCKS AVG_ROW_LEN
------------------------------ ---------- ---------- -----------
EMP                                  1000         28          92

    How to determine if dictionary statistics are RDBMS-generated or user-defined

    The following section explains how to determine if your dictionary statistics are RDBMS-generated or set by users through one of the DBMS_STATS.SET_xx_STATS procedures. This is crucial for development environments that are testing the performance of SQL statements with various sets of statistics. The DBA will need to know if the relying statistics are RDBMS-defined or user-defined.

    RDBMS-generated statistics are generated by the following:

    User generated statistics are only done through the use of the DBMS_STATS.SET_xx_STATS procedures The column USER_STATS from DBA_TABLES, ALL_TABLES, USER_TABLES displays:

    Categories: dbms_stats, oracle Tags:
    1. Tom
      September 10th, 2010 at 06:12 | #1
      Reply | Quote

      Nice summation of stats.

      Could use an example of how to list the stale tables.

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