oracle database start and stop commands

To query the Oracle tablespace size, follow the following steps: Determine the tablespace name by running the query: SELECT tablespace_name FROM dba_tablespaces; Query the tablespace size by running the query: SELECT sum(bytes) AS total_size, sum(bytes_free) AS available_space, sum(bytes) - sum(bytes_free) AS used_space FROM dba_data_files WHERE tablespace_

Oracle View Encryption allows you to encrypt data in the view, thereby enhancing the security of sensitive information. The steps include: 1) creating the master encryption key (MEk); 2) creating an encrypted view, specifying the view and MEk to be encrypted; 3) authorizing users to access the encrypted view. How encrypted views work: When a user querys for an encrypted view, Oracle uses MEk to decrypt data, ensuring that only authorized users can access readable data.

There are three ways to view instance names in Oracle: use the "sqlplus" and "select instance_name from v$instance;" commands on the command line. Use the "show instance_name;" command in SQL*Plus. Check environment variables (ORACLE_SID on Linux) through the operating system's Task Manager, Oracle Enterprise Manager, or through the operating system.

Uninstall method for Oracle installation failure: Close Oracle service, delete Oracle program files and registry keys, uninstall Oracle environment variables, and restart the computer. If the uninstall fails, you can uninstall manually using the Oracle Universal Uninstall Tool.

There are the following methods to get time in Oracle: CURRENT_TIMESTAMP: Returns the current system time, accurate to seconds. SYSTIMESTAMP: More accurate than CURRENT_TIMESTAMP, to nanoseconds. SYSDATE: Returns the current system date, excluding the time part. TO_CHAR(SYSDATE, 'YYY-MM-DD HH24:MI:SS'): Converts the current system date and time to a specific format. EXTRACT: Extracts a specific part from a time value, such as a year, month, or hour.

Data import method: 1. Use the SQLLoader utility: prepare data files, create control files, and run SQLLoader; 2. Use the IMP/EXP tool: export data, import data. Tip: 1. Recommended SQL*Loader for big data sets; 2. The target table should exist and the column definition matches; 3. After importing, data integrity needs to be verified.

In Oracle, the FOR LOOP loop can create cursors dynamically. The steps are: 1. Define the cursor type; 2. Create the loop; 3. Create the cursor dynamically; 4. Execute the cursor; 5. Close the cursor. Example: A cursor can be created cycle-by-circuit to display the names and salaries of the top 10 employees.

To create a user in Oracle, follow these steps: Create a new user using the CREATE USER statement. Grant the necessary permissions using the GRANT statement. Optional: Use the RESOURCE statement to set the quota. Configure other options such as default roles and temporary tablespaces.