  We performed the timing and spectral studies of a Z source GX 17+2 observed
from Astrosat LAXPC instrument. Cross-Correlation function (CCF) was performed
using soft (3-5 keV) and hard (16-40 keV) X -ray bands across the hardness
intensity diagram and found correlated/anti-correlated hard and soft lags which
seems to be a common feature in these sources. We performed spectral analysis
for few of these observations and found no consistent variation in the spectral
parameters during the lags, however 10-40% change was noticed in diskbb and
power-law components in few of observations. For the first time, we report the
detection of HBOs around $\sim$25 Hz and $\sim$ 33 Hz along with their
harmonics using AstroSat LAXPC data. On comparison with spectral results of HB
and other branches, we found that inner disk front is close to the last stable
orbit and as such no systematic variations are observed. We suggest that the
detected lags are readjustment time scales of corona close to the NS and
constrained its height to be around few tens to hundreds of km. The detected
lags and no significant variation of inner disk front across the HID strongly
indicate that structural variation in corona is the most possible cause of Z
track in HID.
