The post is to illustrate the steps to configure the smtp relay using postfix on CentOS/RHEL 5 and 6. For relaying mail through another smtp server, /etc/postfix/main.cf file has to be configured with "relayhost" parameter which specifies the destination smtp server. 1. Install the postfix rpm if not installed already. # rpm -qa|grep postfix 2. Take a backup of the default configuration: # cp /etc/postfix/main.cf /etc/postfix/main.cf.bkp_default 3. Edit the /etc/postfix/main.cf … [Read more...] about How to configure postifx smtp relay in CentOS/RHEL 5 and 6
How To Setup UDEV Rules For RAC OCR And Voting Devices on Partitions
The Goal How to setup UDEV rules RAC OCR and Voting Devices on different partitions, rather than a raw disk. Let's assume that the disk is sdb, which have 3 partitions: sbd1 sbd2 sdb3 It also applies to partitions over different hard disk. The Solution 1. Find the WWID of the disk: # /sbin/scsi_id -g -u -s /block/sdb SATA_VBOX_HARDDISK_VBbb8af1a8-4d4db09b_ Here we got an WWID of 'SATA_VBOX_HARDDISK_VBbb8af1a8-4d4db09b_'. 2. Create an custom UDEV rule: Create a new rule under … [Read more...] about How To Setup UDEV Rules For RAC OCR And Voting Devices on Partitions
How to Change Kernel Semaphore Limits in CentOS/RHEL
The post explains how kernel semaphore limits can be changed in a CentOS/RHEL server. Kernel Parameters to set semaphore limits The kernel parameters to set the semaphore limits are: kernel.sem = SEMMSL SEMMNS SEMOPM SEMMNI SEMMSL - max semaphores per array SEMMNS - max semaphores system wide SEMOPM - max ops per semop call SEMMNI - max number of arrays Changing Semaphore Limits If a limit needs to be changed there should be taken in to account that (max number of arrays)*(max … [Read more...] about How to Change Kernel Semaphore Limits in CentOS/RHEL
Oracle Database Basics – User Accounts
To access the database, a user must specify a valid database user account and successfully authenticate as required by that user account. Each database user has a unique database account. Oracle recommends this to avoid potential security holes and provide meaningful data for certain audit activities. However, users may sometimes share a common database account. In these rare cases, the operating system and applications must provide adequate security for the database. Each user account … [Read more...] about Oracle Database Basics – User Accounts
How to disable or enable an HBA without reboot under CentOS/RHEL
Question: How to Enable or disable HBA ports temporarily, without a reboot? 1. Locate the HBA address on the PCI bus: # lspci -k ... 19:00.0 Fibre Channel: QLogic Corp. ISP2532-based 8Gb Fibre Channel to PCI Express HBA (rev 02) Subsystem: QLogic Corp. Device 0171 Kernel driver in use: qla2xxx 19:00.1 Fibre Channel: QLogic Corp. ISP2532-based 8Gb Fibre Channel to PCI Express HBA (rev 02) Subsystem: QLogic Corp. Device 0171 Kernel driver in use: … [Read more...] about How to disable or enable an HBA without reboot under CentOS/RHEL
Oracle Database Storage Architecture – Overview
The files that comprise an Oracle database are as follows: Control files: Each database has one unique control file that contains data about the database itself (that is, physical database structure information). Multiple copies may be maintained to protect against total loss. It can also contain metadata related to backups. The control file is critical to the database. Without the control file, the database cannot be mounted or opened. Data files: Contain the user or application data of … [Read more...] about Oracle Database Storage Architecture – Overview
Oracle RMAN Pluggable Database Point in Time Recovery
Point in time recovery of a Pluggable Database (from hereon referred to as a PDB) requires ALL files including UNDO to be restored and recovered to the specified time. As all PDBs write to the ROOT UNDO tablespace, point in time recovery of a PDB will use an auxiliary instance and will restore the CDB$ROOT UNDO, SYSTEM, SYSAUX, and SYSEXT tablespaces into the ROOT of the auxiliary instance. The datafiles of the PDB itself are restored and recovered in-situ. The auxiliary database is created … [Read more...] about Oracle RMAN Pluggable Database Point in Time Recovery
Oracle RMAN 12c – New Features
This post provides information on enhancements available in RMAN within Oracle 12c. Support for Container and Pluggable Databases RMAN in 12c provides full backup and recovery support for a Pluggable Database environment. You can perform the backup of the entire container database (CDB), either full or using an incremental backup strategy, or one/many pluggable databases (PDB). SYSBACKUP Privilege In 12c, Oracle support for separation of database administration (DBA) duties by … [Read more...] about Oracle RMAN 12c – New Features
Oracle Database Server Architecture: Overview
Memory Structures There are three major structures in Oracle Database server architecture: memory structures, process structures, and storage structures. A basic Oracle database system consists of an Oracle database and a database instance. The database consists of both physical structures and logical structures. Because the physical and logical structures are separate, the physical storage of data can be managed without affecting access to logical storage structures. The instance … [Read more...] about Oracle Database Server Architecture: Overview
Anonymous User Fails to Upload File to VSFTP Server
The Problem Log into vsftp server with anonymous user from ftp client, try to upload a file fails with error message: # ftp vsftpsrv Connected to vsftpsrv (10.182.38.176). 220 (vsFTPd 2.0.5) Name (10.182.38.176:root): anonymous 331 Please specify the password. Password: 230 Login successful. Remote system type is UNIX. Using binary mode to transfer files. ftp> pwd 257 "/" ftp> ls 227 Entering Passive Mode (10,182,38,176,29,34) 150 Here comes the directory listing. drwxr-xr-x 2 … [Read more...] about Anonymous User Fails to Upload File to VSFTP Server