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Observe the indicators and check the connection consumption --View session session: select * from v$session where username is not null select username,count(username) from v$session where username is not null group by username --View current connections select count(*) from v$process; --View maximu ...

1. Use scenario Both DBMS SQL package and EXECUTE IMMEDIATE in oracle can be used to parse and execute / dynamic SQL statements or PL/SQL blocks created at non runtime. In comparison, EXECUTE IMMEDIATE is relatively simple to use and can meet more common needs. 1.1 basic data CREATE TABLE stu( ID NUMBER(10), xm V ...

Download MySQL installation [root@localhost ~]# cd /home/data/ [root@localhost data]# ls get-docker.sh nginx-1.10.1 nginx-1.10.1.tar.gz redis-5.0.3 redis-5.0.3.tar.gz server-jre-8u131-linux-x64.tar.gz zookeeper-3.4.10.tar.gz [root@localhost data]# wget https://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm If prompted ...

Before 2020, date formatting also provided programmers with a cross-year bug. I wonder if your system is experiencing any? Near the New Year's Day of 2020, many websites show dates like 2020/12/29, 2020/12/30, 2020/12/31.Amazing no?Even the subscription number assistant tool provided by WeChat has made this error. The next two pictures are from ...

Composite partition is the partition of each partition in the partition table. The sub partition can use either HASH partition or KEY partition. This is also known as a subarea. Tip: mysql can only use HASH/KEY partition for sub partition, which is also different from ORACLE. The following issues need to be noted for composit ...

Recently, an error "error: cannot fetch last explain plan from plan" was encountered. Therefore, the following scenarios were studied for details:     1: When you forget to use EXPLAIN PLAN in front of the SQL statement, and then use select * from table (DBMS? Xplan. Display) to view the execution plan of the specific SQL, you will en ...

background Colleagues described that the database orcl instance will be unable to connect in a period of time. It can be used after one restart. It will be unavailable again in about 30 minutes to an hour. Problem finding and troubleshooting ideas For oracle problems, first check the alert.log log View the alert.log log log ...

The so-called parallel execution refers to the ability to physically divide a large serial task (any DML, or general DDL) into several smaller parts, which can be processed at the same time. When to use parallel execution Parallel execution is essentially a non scalable solution designed to allow a single user or each specific SQL statement ...

We want to extract the second order information of all users in descending order according to the user group and the order time of the user. This belongs to group sorting. There are built-in functions in Oracle that can be implemented, but in mysql, it's a bit troublesome: CREATE TABLE user_orders (orders_id INT UNSIGNED NOT NUL ...

When creating a singleton class, consider using enumeration.It addresses issues that may arise due to deserialization and reflection. A singleton is a class that should have only one instance in each JVM.Same instances of a singleton class are reused by multiple threads.In most cases, we use singletons to represent system configurations and wi ...