1. What are the main components of the Goldengate replication?
The replication configuration consists of the following processes.
2. What are the supplemental logging pre-requisites?
The following supplemental logging is required.
- Database supplemental logging
- Object level logging
3. Is there a separate background process for writing flashback logs?
Yes. RVWR (Recovery Writer, Flashback Writer) was introduced in Oracle 10g to write flashback data from the Flashback Buffer in the SGA to the flashback database logs on disk.
4. What command can be used to switch writing the trail data to a new trail file?
You can use the following command to write the trail data to a new trail file.
SEND EXTRACT ext_name, ROLLOVER
5. What happens if RVWR cannot write to disk?
It depends on the context where the write error occurs:
If there’s a Guaranteed Restore Point, the database crashes to ensure the restore point guarantee is not voided.
If there isn’t a Guaranteed Restore Point and it’s a primary database, the Flashback Mode will be automatically turned off for the database, which will be continued to operate normally.
If there isn’t a Guaranteed Restore Point and it’s a standby database, the database will hang until the cause of the write failure is fixed.
6. What type of Topology does Goldengate support?
GoldenGate supports the following topologies;
7. How is the RESTARTCOLLISION parameter different from HANDLECOLLISIONS?
The RESTARTCOLLISION parameter is used to skip ONE transaction only in a situation when the GoldenGate process crashed and performed an operation (INSERT, UPDATE & DELETE) in the database but could not checkpoint the process information to the checkpoint file/table. On recovery, it will skip the transaction and AUTOMATICALLY continue to the next operation in the trail file.
When using HANDLECOLLISION GoldenGate will continue to overwrite and process transactions until the parameter is removed from the parameter files and the processes restarted.
8. Do I need to shutdown and mount the database to turn flashback on?
ALTER DATABASE FLASHBACK ON is an online operation in 11g Release 2. In 10g Release 2, the database must be mounted, but not open.
One flashback is turned on Oracle starts to save the before-images of the database blocks before they are changed. This guarantees that the database can be flashbacked to the exact point in time when the flashback mode was turned on.
9. What are the basic resources required to configure Oracle GoldenGate high availability solution with Oracle Clusterware?
There are 3 basic resources required:
- Virtual IP
- Shared storage
- Action script
10. What transaction types does Goldengate support for Replication?
Goldengate supports both DML and DDL Replication from the source to target.
11. Is there a way to check the syntax of the commands in the parameter file without actually running the GoldenGate process
Yes, you can place the SHOWSYNTAX parameter in the parameter file and try starting. If there is any error you will see it.
12. How can you increase the maximum size of the read operation into the buffer that holds the results of the reads from the transaction log?
If you are using the Classical Extract you may use the TRANSLOGOPTION ASMBUFSIZE parameter to control the read size for ASM Databases.
13. What information can you expect when there us data in the discard file?
When data is discarded, the discard file can contain:
1. Discard row details
2. Database Errors
3. Trail file number
14. How to list restore points in RMAN?
In RMAN you can use the LIST RESTORE POINT [ALL|restore_point_name] command. If you use a recovery catalog you can use the view RC_RESTORE_POINT in the recovery catalog repository, or command the V$RESTORE_POINT in the target database.
15. What database does GoldenGate support for replication?
- Oracle Database
- IBM DB2
- Microsoft SQL Server
16. What are the different encryption levels in AES?
You can encrypt the password/data using the AES in three different keys
a) 128 bit
b) 192 bit and
c) 256 bit
17. How can you determine if the parameters for a process was recently changed
Whenever a process is started, the parameters in the .prm file for the process are written to the process REPORT. You can look at the older process reports to view the parameters which were used to start up the process. By comparing the older and the current reports you can identify the changes in the parameters.
18. How should I set the database to improve Flashback performance?
Oracle’s recommendations are:
Use a fast file system for your flash recovery area, preferably without operating system file caching. It is recommended to use a file system that avoids operating system file caching, such as ASM.
Configure enough disk spindles for the file system that will hold the flash recovery area. For large production databases, multiple disk spindles may be needed to support the required disk throughput for the database to write the flashback logs effectively.
If the storage system used to hold the flash recovery area does not have non-volatile RAM, try to configure the file system on top of striped storage volumes, with a relatively small stripe size such as 128K. This will allow each write to the flashback logs to be spread across multiple spindles, improving performance
For large, production databases, set the init.ora parameter LOG_BUFFER to be at least 8MB. This makes sure the database allocates maximum memory (typically 16MB) for writing flashback database logs.
19. List few useful Logdump commands to view and search data stored in OGG trail files.
Below are a few log dump commands used on a daily basis for displaying or analyzing data stored in a trail file.
$ ./logdump – to connect to the log dump prompt
logdump> open /u01/app/oracle/dirdat/et000001 – to open a trail file in logdump
logdump> file header on – to view the trail file header
logdump> ghdr on – to view the record header with data
logdump> detail on – to view column information
logdump> detail data – to display HEX and ASCII data values to the column list
logdump> recline 200 – to control how much record data is displayed
logdump> pos 0 – To go to the first record
logdump> next (or simply n) – to move from one record to another in sequence
logdump> count – counting records in a trail
20. How would you comment out a line in the parameter file?
You can use the “–” character to comment out a line.