Category Cache taking more time to excute

The below queries taking more time time execute in db i want to know to why these are executing.if these are executing also then taking more time.can we stop to execute these queries due to that my site is always going down on frequent basis.kindly provide anybody solution on priority basis.

Query_time: 30.124537

INSERT INTO cache_category (cid, data, created, expire, headers, serialized) VALUES ('gcmenu_tree_all_dataprimary-links:3777::anonymous user', 'a:1:{s:53:\"cmenu_tree_all_dataprimary-links:3777::anonymous user\";s:37455:\"a:8:{s:17:\"49950 Apparel 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Query_time: 6.132237

INSERT INTO cache_category (cid, data, created, expire, headers, serialized) VALUES ('n3590', 'a:1:{s:25:\"cat_node_get_cats3590:cid\";s:6:\"a:0:{}\";}', 1349934933, 0, '', 1);

Query_time: 10.392684

INSERT INTO cache_category (cid, data, created, expire, headers, serialized) VALUES ('n8331', 'a:1:{s:25:\"cat_node_get_cats8331:cid\";s:6:\"a:0:{}\";}', 1349935101, 0, '', 1);

Query_time: 11.199644
INSERT INTO cache_menu (cid, data, created, expire, headers, serialized) VALUES ('category-menu-trail-links:primary-links:all-cid:6336', 'category-menu-trail-links:primary-links:tree-data:e413fea325d97cafc31d1ce4f0c07910', 1349935101, 0, '', 0);

# User@Host: mystore[mystore] @ web16.intermesh.net [74.84.132.228]
# Query_time: 3.412435 Lock_time: 0.000076 Rows_sent: 0 Rows_examined: 1
SET timestamp=1349936230;
UPDATE sessions SET uid = 1, cache = 0, hostname = '115.111.169.126', session = 'node_overview_filter|a:0:{}', timestamp = 1349936227 WHERE sid = '4v9bnbjm60bgp8d2uirjdh6lk7';

# User@Host: mystore[mystore] @ web16.intermesh.net [74.84.132.228]
# Query_time: 4.725942 Lock_time: 0.000039 Rows_sent: 0 Rows_examined: 1
use test_sourcing;
SET timestamp=1349937022;
UPDATE sessions SET uid = 1, cache = 0, hostname = '115.111.169.126', session = 'node_overview_filter|a:0:{}', timestamp = 1349937018 WHERE sid = '4bd8infj93e0lcrvd838ei2031';