InfoSphere CDC (ISCDC) - FAQ

1. What is Latency in Change Data Capture?
Latency information is normally for Mirroring subscription. As InfoSphere CDC measures latency as the amount of time that passes between when data changes on a source table and when it changes on the target table. For example, if an application inserts a row into the source table at 10:00 and CDC applies that row to the target able at 10:15, then the latency for the subscription is 15 minutes.
2. What is in-scope and out-of-scope tables in InfoSphere CDC terminology?
The tables are inscope tables if they are replicated to the target by InfoSphere CDC. The tables are out-of-scope when those tables are not part of any replication.
3. How to ignore error that occurs during refresh/mirrorring?
Prior 6.3
D_MIRROR_REFRESH_ERROR_STOP=OFF - refresh continues after an error has occurred.
D_MIRROR_MIRROR_ERROR_STOP=OFF - mirroring continues after an error has occurred.
Post 6.3
Set the following 2 system parameters via Management Console.
mirror_end_on_error = false
refresh_end_on_error=false
For more details on these system parameters, please refer IBM InfoSphere Change Data Capture Management Console, Version 6.5 - Administration Guide.
4. Can the source database be read-only for InfoSphere CDC?
Absolutely. Some business demands that the source (which normally are production) database not to be manipulated by any users other than selected one. In such scenario, InfoSphere CDC can very well work with the read-only database.
5. What are the impressions of CDC when the source database is not read-only?
When the source database is not read-only, InfoSphere CDC
  • Adds a table level supplemental logging
  • Turn on the database level tracing
6. Which version of Oracle onwards ISCDC supports log-reading?
Oracle 9 implemented supplemental logging and IS-CDC needs Oracle 9 or later for doing the log reading. Prior version of Oracle 9 did not contain sufficient information to do log based change capture.

7. Why ISCDC enables table level supplemental logging when the source is not read-only?
CDC requires only minimal database supplemental logging. When the source database is not read-only, CDC adds the table level supplemental logging based on the in-scope tables (ie. tables that are mirrored) to reduce the overall impact as database level logging costly interms of generating the logs even for out-of-scope tables.

More will be added ....

Comments

Post a Comment

Popular posts from this blog

Informix 14.10 - EAR - Encryption At Rest (Dbspaces and Backups) with multiple levels of ciphers

Disk Encryption - Operational Data Only Up to IDS 12.10 the encryption was allowed only on the operational data on the dbspaces that the server actively performing read/write operations. The Backup data are not encrypted although there is a provision to give control to the end-user to do it via BACKUP_FILTER and RESTORE_FILTER . IDS does not control any encryption that is done with this method and hence takes no responsibility if the encryption key is lost or due to some other reason the decryption becomes impossible. In order to encrypt the operational data, all needed is to configure the onconfig parameter DISK_ENCRYPTION . It uses keystore file ($INFORMIXDIR/etc/*.p12) and stash file ($INFORMIXDIR/etc/*.sth) to support the encryption. These files are created automatically in 12.10 when DISK_ENCRYPTION is configured. The keystore file is used to store the encryption key and stash file contains the password to open the keystore file where encryption key is stored.  Thes...
Read more

HCL Informix 14.10 - onkstore utility - Remote Key Store

Read my blog on Encryption At Rest (EAR) before this article HCL Informix 14.10 has come up with a new utility called onkstore to generate the keystore (.p12) and stash file (.sth) for types such as local AWS_EAR AWS_BAR Type: local This is provided to store the .p12 and .sth files locally and to have our backward compatibilty with earlier versions which were storing these files locally. These files were essential to perform the encryption of the data and eventually decrypt them when needed. No connectivity to the external AWS site is needed to perform this however since the encryption key files are saved locally on the disk, there is a danger of loosing them and hence loosing the encrypted data that remains encrypted for ever and no way to decrypt them Type: AWS_EAR In order to avoid loosing of the encryption key, we have a new type called AWS_EAR to make sure the encryption key is saved safely and remotely so that can be accessed from amazon web-services, w...
Read more