Which oracle checks

Oracle database is a very popular relational database management system, widely used in enterprise-level information management and data processing. When using Oracle database, it is often necessary to query various information and parameters in the database for debugging, optimization and management. The following will introduce in detail how to view various important information in the Oracle database.

1. View database instance information

1. View instance name

Each instance in the Oracle database has a unique name, which can be passed through the following SQL statement query:

SELECT INSTANCE_NAME FROM V$INSTANCE;

2. View instance version

Oracle database version information is very important for managing and maintaining the database. You can query instance version information through the following SQL statement:

SELECT * FROM V$VERSION;

3. View SGA and PGA information

In the Oracle database, SGA (shared pool) and PGA (private pool) are two important memory areas. The size of SGA and PGA can be queried through the following SQL statement:

SELECT * FROM V$SGA;
SELECT * FROM V$PGASTAT;

4. View database startup time

The startup time of the database is very important for tracking and troubleshooting. You can use the following SQL statement query:

SELECT STARTUP_TIME FROM V$INSTANCE;

5. View the current number of sessions

The Oracle database has very high concurrency and can handle a large number of user requests at the same time. You can query the current number of sessions through the following SQL statement:

SELECT COUNT(*) FROM V$SESSION;

2. View table space information

In Oracle database, table space is an important concept for managing and storing tables and indexes. You can query the size and usage of table space through the following SQL statement:

1. View table space size

SELECT TABLESPACE_NAME, SUM(BYTES)/1024/1024 AS TOTAL_MB,
(SUM(BYTES)-SUM(FREE_SPACE))/1024/1024 AS USED_MB,
SUM(FREE_SPACE)/1024/1024 AS FREE_MB
FROM DBA_FREE_SPACE
GROUP BY TABLESPACE_NAME;

2. View table space usage

SELECT TABLESPACE_NAME,
ROUND(SUM(BYTES)/(1024*1024),2) AS TOTAL_MB,
ROUND((SUM(BYTES)-SUM(FREE_SPACE))/(1024*1024),2) AS USED_MB,
ROUND(SUM(FREE_SPACE)/(1024*1024),2) AS FREE_MB,
ROUND((SUM(BYTES)-SUM(FREE_SPACE))/SUM(BYTES)*100,2) AS USED_PCT
FROM DBA_FREE_SPACE
GROUP BY TABLESPACE_NAME;

3. View database object information

1. View table information

The table is the most basic data storage object in the Oracle database and can be queried through the following SQL statement Information about a table:

SELECT TABLE_NAME, TABLESPACE_NAME, NUM_ROWS, BLOCKS, LAST_ANALYZED
FROM USER_TABLES
WHERE TABLE_NAME = '表名';

2. View index information

Index is an important mechanism in Oracle database for accelerating queries. You can query an index through the following SQL statement Information:

SELECT INDEX_NAME, TABLE_NAME, UNIQUENESS, BLEVEL, DISTINCT_KEYS, LAST_ANALYZED
FROM USER_INDEXES
WHERE INDEX_NAME = '索引名';

3. View view information

A view is a type of database object. You can query the information of a view through the following SQL statement:

SELECT VIEW_NAME, TEXT_LENGTH
FROM USER_VIEWS
WHERE VIEW_NAME = '视图名';

4. View the SQL execution plan

SQL execution plan is an important tool for optimizing the performance of SQL statements. In the Oracle database, you can query it through the following SQL statements:

EXPLAIN PLAN FOR SELECT * FROM 表名 WHERE 条件;
SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY);

5. View the database Parameter information

In Oracle database, there are many parameters that can be configured and adjusted to optimize database performance and functionality. You can query database parameter information through the following SQL statement:

SHOW PARAMETERS;

The above are the methods and statements for viewing various important information in the Oracle database. Mastering these skills can help DBAs better manage and optimize Oracle databases.

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