Hi Sagar, > May I know what is the RAM of server and how much shmmax is configured ? > You can check if any Zombi or defunct process are running on the server. > I want to know if any maintenance activity performed same time? Thanks for you reply. Server has 16GB of RAM. Kernel shmmax has strange value, i think it's default on Ubuntu - i haven't changed that. kernel.shmall = 18446744073692774399 kernel.shmmax = 18446744073692774399 kernel.shmmni = 4096 I changed kermel.sem from defaults to: 250 512000 100 2048 There is no zombi nor defunct process. Now i have 3 stucked processes. First: psql01:~# strace -ffp 14135 Process 14135 attached select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) semop(58261738, {{12, -1, 0}}, 1) = 0 semop(58261738, {{12, -1, 0}}, 1) = 0 semop(58261738, {{12, -1, 0}}, 1) = 0 select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) semop(58261738, {{12, -1, 0}}, 1) = 0 semop(58261738, {{12, -1, 0}}, 1) = 0 semop(58261738, {{12, -1, 0}}, 1) = 0 semop(58261738, {{12, -1, 0}}, 1) = 0 semop(58261738, {{12, -1, 0}}, 1) = 0 select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) Second: psql01:~# strace -ffp 12712 Process 12712 attached select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) semop(57737434, {{6, 1, 0}}, 1) = 0 semop(57934048, {{2, -1, 0}}, 1) = 0 semop(57802972, {{7, 1, 0}}, 1) = 0 semop(57934048, {{2, -1, 0}}, 1) = 0 select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) semop(57934048, {{2, -1, 0}}, 1) = 0 select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) semop(57934048, {{2, -1, 0}}, 1) = 0 semop(57934048, {{2, -1, 0}}, 1) = 0 Third: psql02:~# strace -ffp 18283 Process 18283 attached semop(58523890, {{11, 1, 0}}, 1) = 0 semop(57802972, {{9, -1, 0}}, 1) = 0 select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) semop(57802972, {{9, -1, 0}}, 1) = 0 semop(58818811, {{13, 1, 0}}, 1) = 0 semop(57802972, {{9, -1, 0}}, 1) = 0 select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) semop(57802972, {{9, -1, 0}}, 1) = 0 select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout) perf top: 17.04% postgres [.] _bt_moveright 13.39% postgres [.] LWLockAcquire 8.82% postgres [.] LWLockRelease 8.11% postgres [.] _bt_checkpage 6.10% postgres [.] hash_search_with_hash_value 4.35% libc-2.19.so [.] __strcoll_l 3.16% postgres [.] 0x00000000002989ec 2.06% postgres [.] s_lock 1.99% postgres [.] _bt_compare 1.49% postgres [.] hash_any 1.41% postgres [.] 0x0000000000298a10 1.14% postgres [.] varstr_cmp 1.07% [kernel] [k] _raw_spin_unlock_irqrestore 1.00% libc-2.19.so [.] strlen 0.99% postgres [.] 0x0000000000298fdb 0.96% postgres [.] 0x00000000002989fc 0.80% postgres [.] LockBuffer 0.73% libc-2.19.so [.] 0x000000000009478e 0.60% postgres [.] ReadBufferExtended 0.49% postgres [.] bttextcmp 0.47% libc-2.19.so [.] 0x0000000000094787 0.44% [kernel] [k] finish_task_switch 0.40% postgres [.] _bt_relandgetbuf 0.40% postgres [.] ResourceOwnerForgetBuffer 0.40% libc-2.19.so [.] 0x0000000000094782 0.39% postgres [.] FunctionCall2Coll 0.38% postgres [.] ReleaseAndReadBuffer 0.31% postgres [.] pg_detoast_datum_packed Best regards, Michal -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin