Disable file system caching for Db2 Linux on IBM Z®

When running an instance of Db2 on an IBM Z Linux, you need to enable the DB2_DIRECT_IO registry variable to ensure data integrity.

About this task

The DB2_DIRECT_IO registry variable ensures that disk writes are written directly to disk without use of file system caching. You need to enable the DB2_DIRECT_IO registry variable before you create or activate a database on Db2 Linux on IBM Z .

Procedure

Run the following commands as instance owner:
```
db2stop
db2set DB2_DIRECT_IO=ON
db2start
```
Verify the registry variable is set in the instance by running the following command:
```
db2set
```
For example:
```
$ db2set DB2_DIRECT_IO=ON
$ db2set
DB2RSHCMD=/usr/bin/ssh
DB2_DIRECT_IO=ON
DB2COMM=TCPIP
```