How to Run Data Consistency Checks with SAPDBA 
Purpose
Consistency checks on your Informix database can take a long time to perform and might sometimes impact system performance. Therefore, it makes sense to identify high-risk data and do checks that you can fit into the time available. This section looks at how to choose the:
- Type of check (that is, whether to use ONCHECK and whether to check "blob" fields)
- Level of check (that is, whether to check a single table, all R/3 tables, and so on)
- Frequency of checks and when to run them
- Tool to use, SAPDBA or the Computing Center Management System (CCMS)
Process Flow
You decide on the type of check. Consider the following:
- Remember that the Check ... actions are a more thorough way of checking the physical data consistency of tables than the ONCHECK ... actions. However, the Check ... actions take longer to perform since all data is examined with a read operation.
- The riskiest type of data is in "blob" fields. Therefore, there are several actions available that only examine the tables with blob fields. It makes sense to run checks on your blob data more often than on other types of data.
- You decide on the level of check. Consider the following:
Checking All Tables of R/3 Database for Data Consistency with SAPDBA is a very time-consuming procedure depending on the size of the database.
Checking Tables of a Dbspace for Data Consistency with SAPDBA breaks up the task of checking the entire database. You need to perform it once for each dbspace in the database. Do not forget any dbspaces.
- You decide when to run the checks and how often. You need to make sure that you have at least one level-0 database backup (
ON-Bar
) or archive (
ON-Archive
and
ontape
) containing data which you have checked for consistency. Refer to
Database Backup (ON-Bar) or
Archive (ON-Archive and ontape). Therefore, it is best to run a data consistency check on all data in the R/3 database as often as you can before a level-0 database backup or archive.
Consistency checks have an impact on database performance. Therefore SAP recommends that you schedule them for off-peak periods, for example, at weekends or overnight. If the performance of your system is affected during a consistency check, you can stop the check and then restart it later.
You decide if you want to use the DBA Planning Calendar in CCMS to schedule the check. Refer to
Checking Physical Consistency in the DBA Planning Calendar (Informix). It is not possible to schedule checks with SAPDBA.
Result
Your database data is checked for consistency in the best way, with the least possible impact on your production system.