Assume there is an application in a non-stop loop trying to read from database.
I have tried the following but it does not work:
db2 CONNECT TO SAMPLE
db2 QUIESCE DATABASE IMMEDIATE FORCE CONNECTIONS
db2 TERMINATE
db2 DEACTIVATE DB SAMPLE
db2 BACKUP DATABASE SAMPLE
It seems as if (DEACTIVATE DB) does not do anything since an application in a loop can still read from the database.
I keep getting the error "The database is currently in use" when trying to backup.
You have to make sure there are not applications connected to the database (db2 list applications). Also, you have to make sure the database is not active (db2 list active databases).
Remember that a quiesce or a force applications, is a asynchronous task. It means that you execute any of them, but when the control is returned it does not mean the applications have bee disconnected.
A typical case is a rollback of a batch process, when the rollback takes several minutes.
QUIESCE DATABASE will not prevent new connections from coming in. I believe you have at least two choices:
Use QUIESCE INSTANCE <instance> USER <username> RESTRICTED ACCESS IMMEDIATE FORCE CONNECTIONS. This will force all existing connections and restricts access for new connections. Only the user specified in USER will be able to connect. Presumably, this will be your administrative account.
If this is a no-go, or if you are unable prevent USER from spawning new connections, you may want to (temporarily) UNCATALOG DB and/or disable the DB2COMM registry variable in order to prevent new connections.
HTH.
Related
I have a few PCs that have local PostgreSQL databases running, just logging data. Data is only ever inserted, never removed or updated. The remote PCs are connected to the internet by cellular modem and depending on their location, often do not have internet access. When they do have an internet connection I would like them to push a copy of their databases to a central location and keep the remote database up to date with any new data. Essentially, I need an 'rsync' for databases.
At first it seemed like what I need is to set up PostgreSQL Hot-Standby but I'm unsure if this is actually what I need because my situation seems to differ from the examples I've seen.
Each remote PC has a Postgres server with a single database that has a unique name, the tables within the DBs have generic names. I would like to synchronize these databases to a single remote Postgres server. I think this should be okay due to the unique DB names.
My connectivity is very intermittent, days to weeks without a connection. I've seen PgAdmin be very reliable despite a terrible (cellular) internet connection, if Postges Hot-Standby is the same I may be alright.
As far as I can see my options are either to set up PostgreSQL Hot-Standby, or roll my own solution. I don't want to roll my own solution. However it is simple enough if I can't find anything better; a Python daemon run by systemd to find the diff between the local and remote DB, then push the new rows from the local to the remote DB. But I'm sure someone has solved this problem, I just haven't found the solution yet.
You don't need hot standby (which is the PostgreSQL term for being able to query the replicated database), but streaming replication. You need a central standby server for each intermittently connected remote database server. If you use replication slots, you can be sure that replication will never fall behind.
I'm using several connections in SQL developer to connect to different Oracle databases. For some connections I have to change the schema to that of another user. This can be done is several ways
By using: alter session set current_schema = <otheruser>;
The drawback is that I have to enter this for every connection I want to open and with a different <otheruser> for each connection.
Using the global connection startup script in Preferences > Database > Filename for connection startup script. The drawback of this method is that SQL Developer uses the same global startup script and runs it for every connection I open. Probably trying to set a non existing schema in most -but one- connections.
Is there a way to automatically set the default schema on connecting to a database for individual connections?
Connection Schema
conn_1 Leave current schema unchanged for this connection
conn_2 Change current schema to <schema_A> for this connection
conn_3 Leave current schema unchanged for this connection
conn_4 Change current schema to <schema_B> for this connection
conn_5 Change current schema to <schema_C> for this connection
A solution will be very helpful.
No, that is not a feature. We assume when you define the connection, you are using the schema that you want to work with.
The tool is VERY connection driven - using alter session set current schema will work with queries you run in a SQL Worksheet, but won't have any effect for the rest of the tool, say browsing your tables in the Connection navigation tree.
Now, if you have PROXY connect privs, you could set up your connection to actually connect to your 'default' schema via proxy.
I show how here
I am new to Oracle databases(I am using Oracle Database 11g Express Edition) and sqldeveloper. I have this doubt
When creating a new connection in sqldeveloper what is actually happening?
Creating a new database or connecting to an existing databasE?
If I create multiple connections are they pointing to a single database or different databases, if the later then how to choose a database name while creating a connection
You are establishing a connection to user (i.e. schema) which resides in an (Oracle) database. One database contains many users, so - create one connection per user.
Creating a connection does NOT create a new database; it is done differently. I don't think that 11gXE offers that option; you'd need a Standard or Enterprise Edition.
No problem if you use multiple databases (most of us do). I prefer keeping them in TNSNAMES.ORA file, in a directory used by the TNS_ADMIN environment variable. Currently, there are 94 databases I have access to, each of them having many users.
In your case, 11gXE is (probably) installed on your own computer, and you'll use one of its users (HR?), so - just connect to it. If it is locked, you'll have to unlock it first, though - in that case, create connection to SYS (don't forget to connect AS SYSDBA), then
ALTER USER hr ACCOUNT UNLOCK;
ALTER USER hr IDENTIFIED BY hr;
and then create connection to "hr" whose password is now set to "hr" (all lower case).
Is it possible to access, particularly insert into, a database while it's being restored by pg_restore from a custom format.
If yes, then should I care about preventing clients from accessing the database while pg_restore is running, or the restore operation is "transactional" so that after it ends all changes made by clients since its start will be lost?
If you want to keep concurrent sessions out of your database during pg_restore, you'll have to block them with a pg_hba.conf entry.
There is no protection from concurrent sessions inserting or otherwise modifying data while pg_restore is running.
Is it possible to edit firebird database, alter trigger without connecting to it, using raw .fdb file or .gbak?
Although with sufficient knowledge of the internal structure of Firebird it would be possible to edit the file directly, in practice that is not a viable way (and would be a great way to corrupt your database).
Users with admin rights can disable firing database triggers on connect for a connection, see also Database Triggers.
For example when you use ISQL, you can start it with isql -nodbtriggers. This only works with SYSDBA, or if you have the RDB$ADMIN role and if you specify that role on connect.