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Archives for May 2019

How to check the status and space used by images and containers

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This post objective is to find out the stats of running container, system information related to space used by images and containers on /var/lib/docker. 1. 'docker stats' command used to check the containers stats on system like CPU usage, IO usage, Memory usage. Below example is for 2 running containers dockerweb and webserver2. # docker stats dockerweb webserver2 CONTAINER ID NAME CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS e33f00e0e3ce dockerweb … [Read more...] about How to check the status and space used by images and containers

How to Resize the Undo Tablespace in Oracle Database

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This post provides the steps to resize the Undo tablespace.ie, to add space or shrink the current Undo tablespace. Shrinking Undo Tablespace Size Undo space once allocated will be available for reuse but will not be deallocated to the OS. The best way to shrink Undo tablespace is to switch to a new Undo tablespace and drop the old Undo tablespace. The steps are: 1. Create a new undo tablespace of the same size (larger or smaller) depending on your database requirements. SQL> create undo … [Read more...] about How to Resize the Undo Tablespace in Oracle Database

How to Shrink the datafile of Undo Tablespace in Oracle Database

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Your production database has semiannual or annual purging programs which generate huge redo. Due to this requirement, your undo tablespace grows rapidly and occupies most of the space on the file system. The purging process is run only a few times a year. So would not like to keep the huge undo datafile in your database throughout the year. You don't want to buy additional disks unnecessarily. You have created an undo tablespace with datafiles as AUTOEXTEND ON MAXSIZE UNLIMITED to avoid the … [Read more...] about How to Shrink the datafile of Undo Tablespace in Oracle Database

How to Drop Undo Tablespace in Oracle Database

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This post provides the steps to drop an Undo tablespace. The Undo tablespace can be dropped if it is not the default Undo tablespace of the database and all the Undo segments in it are OFFLINE. 1. check whether the Undo tablespace to be dropped is the default Undo tablespace: sql> show parameter undo The tablespace name mentioned by the parameter UNDO_TABLESPACE is the current default Undo tablespace. 2. If the UNDO_TABLESPACE is set to the one to be dropped, create a new Undo … [Read more...] about How to Drop Undo Tablespace in Oracle Database

Unable to Drop Undo tablespace Since Undo Segment is in Needs Recovery

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The Problem New Undo tablespace was created and a attempt is made to drop old undo tablespace. Dropping the old Undo tablespace give message: ORA-01548: active rollback segment Or Undo segment shows status as needs recovery The Solution The issue could happen if the datafile on which the undo segments reside is offline and the transaction cannot be rolled backed since the file is offline or this could also happen if there is any issue in the Undo segment itself. Check Undo … [Read more...] about Unable to Drop Undo tablespace Since Undo Segment is in Needs Recovery

How to Switch to a New Undo Tablespace in Oracle Database

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This post explains the steps to switch to a new Undo tablespace. 1. Check your current default Undo tablespace: SQL> show parameter undo_tablespace 2. Determine the size of the datafile(s) for your current undo tablespace: sql> select tablespace_name, file_id, file_name,round (bytes / (1024 * 1024), 0) total_space from dba_data_files where tablespace_name=[tablespace_name from the above output]; For example: sql> select tablespace_name, file_id, file_name,round (bytes / (1024 * … [Read more...] about How to Switch to a New Undo Tablespace in Oracle Database

When to Use Startup/Shutdown Database and Alter Database Command in Oracle 12c

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Before 12c there are only few commands available for startup and shutdown but if we follow that we may end up starting and stopping the PDBs and CDB as well. shutdown normal shutdown immediate shutdown abort startup startup nomount startup mount If we use one of these traditional shutdown methods at the container database (CDB) layer, we will bring down the CDB and the associated PDBs under it. This is something to be aware of when looking to reboot a container database. Let's take a … [Read more...] about When to Use Startup/Shutdown Database and Alter Database Command in Oracle 12c

How to Startup/Shutdown PDB’s in Oracle Database 12c

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Traditional startup/shutdown methods prior to 12c Traditional startup/shutdown command prior to 12c as as shown below. Shutdown Command SHUTDOWN NORMAL SHUTDOWN IMMEDIATE SHUTDOWN ABORT Startup Command STARTUP STARTUP NOMOUNT STARTUP MOUNT What happen when we execute shutdown immediate at CDB? If we use one of these traditional shutdown methods at the container database (CDB) layer, we will bring down the CDB and the associated PDBs under it. $ sqlplus / as sysdba SQL*Plus: … [Read more...] about How to Startup/Shutdown PDB’s in Oracle Database 12c

How to Remove/ Disable Bash shell Command History on Linux

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This post will help you to remove/ disable Bash shell commands history on Linux. 1. Disable history for a current shell. # set +o history 2. Clean command history. # history -c 3. Permanently disable bash history. # echo 'set +o history' >> ~/.bashrc Next time when user login to the shell it will not store any commands to a history file .bash_history. To apply this settings immediately for the current shell session execute the .bashrc file: # . ~/.bashrc 4. Disable a … [Read more...] about How to Remove/ Disable Bash shell Command History on Linux