ORA-01555: snapshot too old usually means Oracle could not reconstruct the older version of data needed by a query because the required undo information was no longer available. Why it happens A long-running query needs older row versions while other sessions keep changing the same data. The undo tablespace is too small for the workload. … Read more
How file permissions are changed on an FTP or hosting server, with safer modern notes.
How to reinstall GRUB from a Linux rescue environment after bootloader problems.
This is a legacy note for Oracle 10g R2. The old companion-disk workflow is specific to that release and should not be treated as the installation method for current Oracle Database versions. Oracle 10g R2 workflow Install the sample-schema components supplied for the 10g R2 release. Connect as a suitably privileged database user. Run the … Read more
A no. of errors are encountered while importing dump files in Oracle database.
Some of them are due to
1. Tablespace not found.
2. User/Role not found.
3. Incorrect database charset
If correct parameters are not provided to the person doing the import, it a more of HIT/TRIAL methdology.
Try using this query to identify the approach to attack invalid objects in the schema select referenced_name, count(referenced_name) cnt from user_dependencies where referenced_name in (select distinct object_name from user_objects where status = ‘INVALID’) group by referenced_name order by cnt desc This will list down the objects in descending order on which maximum no. of invalid objects … Read more
Not able to connect to the DB.
Error Messages encountered:
TNS-03505:
Failed to resolve name
ORA-12154:
TNS:could not resolve the connect identifier specified
The possible solutions can be
Oracle sequences generate numeric values independently of a table and are commonly used for surrogate keys, batch identifiers, and other incrementing values. Create and use a sequence CREATE SEQUENCE supplier_seq START WITH 1 INCREMENT BY 1 CACHE 20; INSERT INTO suppliers (supplier_id, supplier_name) VALUES (supplier_seq.NEXTVAL, ‘Example’); NEXTVAL gets the next value. Gaps are normal and … Read more
The SQL*Plus COPY command is a legacy way to copy query results between Oracle databases or schemas. It can still matter in older environments, but newer workflows usually use database links, CREATE TABLE AS SELECT, Data Pump, or application-level migration tools. Legacy COPY syntax COPY FROM user1/password@db1 TO user2/password@db2 CREATE destination_table USING SELECT * FROM … Read more
Oracle performance tuning starts by identifying where time is actually being spent. For SQL statements, execution plans, SQL statistics, and active-session data are usually more useful than guessing from source code. For PL/SQL, profiling tools can show which procedures or lines consume the most time. Start with SQL-level evidence Inspect the execution plan with DBMS_XPLAN. … Read more