If you are updating DB2 Express C on Linux to newly released 9.7.4 version, follow my instructions in older blog post.
If you are using db2 text search, it will fail after update with error message:
CIE00340 Cannot start executable program "/bin/sh".
You need to update db2 text search instance as well by running:
configTool upgradeInstance -configPath sqllib/db2tss/config \
If you put entire command on single line, omit \