Oct 12 2016

Oracle 11g Oracle Checkpoint Not Complete, Cannot Allocate New Log Warning

Category: Administration,Errors and SolutionsFatih Acar @ 11:54

Error: Checkpoint not complete, Cannot Allocate New Log Warning

Thread 1 cannot allocate new log, sequence 125487
Checkpoint not complete

Solution: Checkpoint not complete messages are generated due to the logs are switching so fast that the checkpoint associated with the log switch isn’t complete. You should increase redo log file size and amount to resolve. Also, If you use archive_lag_target parameter as near zero for example like 1 or 2 minutes, you should change this parameter zero (no lag) or more than 10-15 min. Oracle recommends that redo log switch operation interval should be between 15-30 minutes.


Show and change archive_lag_target parameter

SQL> show parameter archive_lag_target;
SQL> alter system set archive_lag_target=0 scope=both;
SQL> alter system set archive_lag_target=1800 scope=both;
1800 is 15 minutes. Parameter value as second.

If your archive_lag_target parameter is normal and you get checkpoint not complete error, you have to look your redo log file size and amount.
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Tags: Oracle Error Solutions

Sep 27 2016

Keep Table in Buffer Pool Oracle 11g

Category: AdministrationFatih Acar @ 09:35

Oracle provides a feature to keep objects in the Buffer pool. This feature allows you to keep the frequently accessed table in memory itself which will provide the faster access of the table. The object will be kept under the KEEP pool and the purpose of the keep pool is to accommodate / cache the small objects like look up tables.

In general the server process has to bring data blocks for the table from the disk to the memory (buffer pool) which requires an overhead. Moreover the object gets removed from the memory whenever the object is not getting used or oracle needs room for another table in the buffer pool. If you keep the frequently accessed objects in the memory the above mentioned overhead can be reduced.

Keep Buffer is also working in First In First Out mode. If Oracle has more objects to keep in the KEEP buffer, automatically it removes the older objects from the keep buffer.  DB_KEEP_CACHE_SIZE is the parameter which determines the size of the Keep Buffer Pool. If this parameter is 0, Oracle adjust automatically size.

Keep Table in Buffer Pool

SQL> alter table testtable storage (buffer_pool keep);

Table altered.

Continue reading “Keep Table in Buffer Pool Oracle 11g”

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Tags: Database Administration, Oracle Administration

Aug 23 2016

Create Dblink From Oracle to PostgreSQL Database

Category: Administration,AdministrationFatih Acar @ 14:36

Since fetching data from PostgreSQL database to Oracle database, you can create database link between two database systems. For that you can apply below operations.

Test Systems

PostgreSQL DB
IP :
OS : Centos 7 x64
Service : postgresql.service

Oracle DB
IP :
OS : OEL 6 x64


PostgreSQL Side

psql# create user dblinkuser encrypted password ‘dblinkuserpass’;

psql# grant usage on schema “testschema” to dblinkuser;

psql# grant select on “testschema”.tbl_test to dblinkuser;

Add new line to pg_hba.conf

vi /pgdir/data/pg_hba.conf

host testdb dblinkuser md5

systemctl reload postgresql.service

Oracle Side

yum install postgresql-odbc

vi /etc/odbc.ini

Description = PG
Driver = /usr/lib64/psqlodbc.so
ServerName =
Username = dblinkuser
Password = dblinkuserpass
Port = 5432
Database = testdb
Driver = /usr/lib64/liboplodbcS.so

vi $ORACLE_HOME/hs/admin/initPG.ora

# This is a sample agent init file that contains the HS parameters that are
# needed for the Database Gateway for ODBC

# HS init parameters
HS_FDS_SHAREABLE_NAME = /usr/lib64/psqlodbc.so
# ODBC specific environment variables
set ODBCINI=/etc/odbc.ini

# ODBC specific environment variables

# Environment variables required for the non-Oracle system
#set =

vi $ORACLE_HOME/network/admin/tnsnames.ora

PG =
(SID = PG)
(HS = OK)

vi $GRID_HOME/network/admin/listener.ora


lsnrctl reload

Listener reload can be adacuate to apply changes;but, sometimes not.

lsnrctl stop
lsnrctl start
lsnrctl status

Create Database Link on Oracle

CONNECT TO “dblinkuser”
IDENTIFIED BY ‘dblinkuserpass’


select * from “testschema”.”tbl_test”@PG

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Tags: Database Administration, Oracle Administration, PostgreSQL Administration

May 26 2016

Oracle 12c : RMAN New Features and Enhancements

Category: Administration,Backup And RecoveryFatih Acar @ 10:45

 1. Fine Grained Recovery

With Oracle Database 12c, you can use a simple RECOVER TABLE command to perform a point-in-time recovery of a table/partition without having to go through a manual point-in-time recovery process. This command automatically performs the following steps: creation of the auxiliary instance, table recovery, exporting of the object, and importing it into the production database.

2. Support For Multitenant Databases

Oracle Database 12c offers this unprecedented consolidation feature called Oracle Multitenant. This capability simplifies database consolidation and management by enabling many individual pluggable databases (PDBs) to be “plugged-into” and supported within a container database (CDB).  Data protection is greatly simplified because you can perform backup and recovery at the CDB level, which includes and protects all the associated PDBs. For additional flexibility, you can still choose to perform backup and recovery for an individual PDB or a selected group of PDBs.

3. Improved RMAN Duplication (Cloning) Performance

Duplicating an Oracle database can be performed in many ways. Today, customers use both Oracle features such as RMAN DUPLICATE or storage-based snapshot and cloning technologies. RMAN duplication can be performed by using an existing backup or by directly duplicating the database using ACTIVE DUPLICATE.  Prior to Oracle Database 12c,  the ACTIVE DUPLICATE process used production database processes to send image copies across the network. This could be a time-consuming activity because the duplication process is directly proportional to the database size. Now, with 12c, the database duplication process has been improved, with the use of backup sets instead of image copies. As a result, the database size is relatively smaller because RMAN skips unused blocks, committed undo blocks etc. Plus, you can use compression and multi-section options for even faster duplication. Moreover, auxiliary channels from the destination site are used to PULL the backups over the network, as opposed to the PUSH method, used prior to 12c.

4. Faster Recovery in a Data Guard or Active Data Guard Environment

You may already be aware of some cool RMAN features that are supported with Active Data Guard – for example, direct Block Media Recovery from the standby. However, in the event of either primary or standby datafile corruption (e.g. due to media errors), the traditional recovery process would be to copy the backup over the network and perform a restore/recovery.  With Oracle Database 12c, there is a new RMAN keyword called “FROM SERVICE” whereby you can perform restores directly from the standby or from the primary (depending on which site has issues). This command creates a backup set and streams it over the network. This new process dramatically reduces the overall recovery time.

5. Expansion of Multi-Eection Support

Prior to Oracle Database12c, parallelizing a single data file using MULTI SECTION was only supported with a level 0 backup or a full backup set. From 12c, Multi section is now supported with incremental backups as well as image copy backups.

6. Simplified Cross-Platform Migration

Migrating the database from one platform to another can be performed in many ways. Oracle supports both database-level migration and tablespace-level migration. Database-level migration requires the endian type to be same on the source and destination platforms. Using tablespace migration, you can migrate across platforms and across endian formats. Oracle 12c introduces new keywords – FROM PLATFORM and TO PLATFORM. Using these keywords, RMAN takes care of converting the endian-ness,  so that the overall process is simplified. Depending on the availability requirements, tablespace migration can be performed with either long downtime or reduced downtime processes.

a) When using a longer downtime model, you place the tablespace(s) in read-only mode, take the full backup, and restore at the destination. You also take the metadata export of the tablespace at the source and then apply at the destination. Once you’re done, the tablespaces are made readable/writable at the destination.

b) When using a reduced downtime model, you can keep your source database running for a longer time by doing incremental backups to the destination. Only the last step involves the procedure mentioned in (a).

7. Separation of Duty

A new role SYSBACKUP is introduced to separate backup administrator tasks from the SYS role. You can use this administrative privilege to perform backup and recovery operations from either RMAN or from SQL*Plus.

8. SQL interface in RMAN

Beginning with Oracle Database12c, you no longer have to switch between the SQL*Plus interface and RMAN interface. The RMAN interface now supports SQL commands so you can directly run the commands from within RMAN.

Source : Oracle Documents

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Tags: Oracle 12c, Oracle Administration, Oracle Rman Backup

Jan 12 2016

Oracle 11g Data Guard Failover With Python Script

Category: Administration,Backup And Recovery,Linux & Unix,PythonFatih Acar @ 10:56

I wrote a python script to perform failover steps and to take product database IP addresses when product database is down. If you dont use data guard broker or other application for failover operations, you can use this script for failover. My scenario is that I have Oracle 11gR2 2 nodes RAC product database and 1 node standby real time apply type data guard database. When the product database is fail, the data guard database can run as product database with take product database IP addresses and service name. Python script will do all steps that take product IP address, take product service name, perform failover steps.

I made test when data guard was archivelog apply type, script could run correctly.


Product Database : Oracle 11g R2 ( RAC
Data Guard : Oracle 11g R2 ( Single Instance With Grid Infrastructure
Operating System : Oracle Linux 6.6
Data Guard Type : Real Time Apply From Redo Logs
Script Name : failover.py

Python script file is failover.py .Firstly, we have to change parameters in script. You can use vi editor. I generally create python files under /opt/scripts directory.


Script has 3 types take virtual IP process. If you can not see product virtual IP address when you run ifconfig command after run failover.py script, you can use other type virtual IP process.

The product database is fail. We have to run data guard database like product database. We can use failover.py script.

Run failover.py

[root@dg scripts]# python failover.py


If all parameters are correct, you can write “evet” and push enter.

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Dec 02 2015

Move Datafiles Of Tablespaces With RMAN Set Newname in Oracle 11g

Category: Administration,Backup And RecoveryFatih Acar @ 17:30

You can move datafiles of tablespaces. Scenarios can be asm to file system or file system to file system or file system to file system or asm to asm. Below operations show how to move datafiles. You have to take a backup and database has to be archivelog mode before this operations because of that you do restore and recover operation.


1 – Database has to be Archivelog Mode
2 – Take Full Rman Backup
3 – Execute Rman Run block

Run Block Description:
Offline Tablespace.
Set Newname.
Restore Datafile To New Location.
Write New Location information to controlfile with switch datafile all.
Recover Datafile.
Online Tablespace.


List Tablespaces

SQL> select tablespace_name from dba_tablespaces;

List Datafile Directories

SQL> select tablespace_name,file_name from dba_data_files;

Move Datafile From Asm To File System

SET NEWNAME FOR DATAFILE ‘+DATA/dg/datafile/USERS.329.896267113’ TO ‘/tmp/USERS.329.896267113’;

Move Datafile From File System To From Asm
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Nov 15 2015

Auto Increment Primary Key With Trigger in Oracle 11g

Category: Administration,Procedure,SQLFatih Acar @ 14:50

You can provide auto increment primary with trigger by appling below operations.

Create Table

(id number primary key,
name varchar2(100));

Create Sequence

MAXVALUE 999999999

Create Trigger For Auto Increment

before insert on TESTUSER.TBL_TEST
for each row
if inserting then
if :NEW.”ID” is null then
select TESTUSER.SEQ_TEST_ID.nextval into :NEW.ID from dual;
end if;
end if;

Oracle 12c release has primary key auto increment feature with identity type column. You can use like below.
Continue reading “Auto Increment Primary Key With Trigger in Oracle 11g”

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May 28 2015

How to Migrate Controlfile From File System to ASM Disk in Oracle 11g

Category: Administration,Backup And RecoveryFatih Acar @ 13:36

You can migrate controlfile from file system to asm disk. You have to stop database and you can do that.

Stop Database

SQL> shutdown immediate;
SQL> startup nomount;

Migrate Controlfile

RMAN> restore controlfile to ‘+DATA’ from ‘/tmp/controlfile_currentlocation.ctl’;
RMAN> restore controlfile to ‘+FRA’ from ‘/tmp/controlfile_currentlocation.ctl’;

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Tags: Oracle, Oracle Administration, Oracle Backup and Restore

Mar 09 2015

Oracle Cluster Service Control Commands CRSCTL

Category: AdministrationFatih Acar @ 09:54

crsctl is Oracle Clusterware management command. You can check, start, stop clusterware with crsctl. crsctl command directory is $GRID_HOME/bin.

You can do below operations with crsctl

  • Starting and stopping Oracle Clusterware resources
  • Enabling and disabling Oracle Clusterware daemons
  • Checking the health of the cluster
  • Managing resources that represent third-party applications
  • Integrating Intelligent Platform Management Interface (IPMI) with Oracle Clusterware to provide failure isolation support and to ensure cluster integrity
  • Debugging Oracle Clusterware components

List Status Of All Crs Services

crs_stat -t

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Jan 27 2015

How to Change Oracle Enterprise Manager Port Number

Category: Administration,Database SecurityFatih Acar @ 17:29

If you want to change Oracle Enterprise Manager port number, you can use “emca -reconfig ports -DBCONTROL_HTTP_PORT ” command, this is simple. You can use to take security measure for Oracle EM. I will give 1820 as port for Oracle EM as example.

Change Oracle Enterprise Manager Port


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