Pre-migration checklist of diagnostic information

Before you migrate to a newer version of Informix®, gather diagnostic information, especially if you have large, complex applications. This information will be useful to verify database server behavior after migration. This information will also be useful if you need help from Software Support.

If you have problems, you or Software Support can compare the information that you gather with information obtained after migration.

The following table contains a list of the diagnostic information that you can gather. You can print the checklist. Then, after you get the information specified in each row, check the second column of the row.

Table 1. Checklist of information to get before migrating
Information to Get Before Migrating Done
Get the SQL query plans for all regularly used queries, especially complex queries, by using SET EXPLAIN ON.
Run the dbschema -d -hd command for all critical tables.

The output contains distribution information.
Get oncheck -pr output that dumps all of the root reserved pages.
Make a copy of the ONCONFIG configuration file.

A copy of the ONCONFIG file is essential if you need to revert to an earlier version of the database server. In addition, a copy of this file is useful because oncheck -pr does not dump all of the configuration parameters.

Prepare a list of all the environment variables that are set using the env command.

During times of peak usage:

  • Obtain an online.log snippet, with some checkpoint durations in it
  • Run onstat -aF, -g all, and -g stk all.

During times of peak usage, run the following onstat commands repeatedly with the -r repeat option for a period of about three to five minutes:

  • onstat -u, to see the total number of sqlexecs used
  • onstat -p, for read and write cache rates, to detect deadlocks and the number of sequential scans
  • onstat -g nta, a consolidated output of -g ntu, ntt, ntm and ntd
  • onstat -g nsc, -g nsd, and -g nss for the status of shared memory connections
  • onstat -P, -g tpf, and -g ppf
  • vmstat, iostat and sar, for cpu utilization
  • timex of all queries that you regularly run