Vince, thank you for your comment.
ArcGIS Server for Linux is actually 10.1 SP1. Sorry, I should have written it accurately.
and I've checked postgresql version.
It is said:
psql (9.1.5, server 9.1.9)
# select version();
version
--------------------------------------------------------------------------------------------------------------
PostgreSQL 9.1.9 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-54), 64-bit
ArcGIS Server 10.1 SP1 was installed and then PostgreSQL 9.1 was installed. But 9.0 was running so our colleague switched to 9.1 as a main database.
ArcGIS for Desktop is also 10.1 SP1 by the way.
re-installing postgresql-9.1 is only option?