Progress in Organic Coatings ,Volume 66, Issue 3,Pages 199-205
Progress in Organic Coatings 66 (2009) 199–205
Contents lists available at ScienceDirect
Progress in Organic
Coatings
j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /p o r g c o a
t
Composite anticorrosion coatings for AZ91D magnesium alloy with molybdate conversion coating and silicon sol–gel coatings
Junying Hu,Qing Li ?,Xiankang Zhong,Liang Zhang,Bo Chen
School of Chemistry and Chemical Engineering,Southwest University,Tiansheng Road,Chongqing 400715,China
a r t i c l e i n f o Article history:
Received 14November 2008
Received in revised form 18February 2009Accepted 22July 2009Keywords:
Magnesium alloy Molybdate Silicon sol–gel
Corrosion resistance
a b s t r a c t
This study evaluated the corrosion resistance of AZ91D magnesium alloy coated by composite coatings which consisted of a molybdate conversion coating and three layers of silicon sol–gel coatings.For molyb-date conversion treatment,various conditions including the pH of the molybdate baths,immersion time and bath temperature were investigated using electrochemical measurements.The corrosion resistance of the AZ91D magnesium alloy was improved to some extent by the conversion coating with the optimal conversion parameters (7.3g/L (NH 4)6Mo 7O 24·6H 2O solution with pH 5for 30min at 30?C).
In order to get a further improvement of corrosion protection for AZ91D magnesium alloy,three layers of silicon sol–gel coatings were successfully deposited on the molybdate conversion coating pre-applied to AZ91D alloy.The surface morphology and the corrosion protection performance of the composite coatings were investigated in detail using scanning electron microscope,electrochemical impedance spectroscopy as well as potentiodynamic polarization tests.The results demonstrated that the composite coatings could greatly improve the corrosion protection performance of the AZ91D magnesium alloy.
? 2009 Elsevier B.V. All rights reserved.
1.Introduction
Magnesium and magnesium alloys exhibit an attractive combi-nation of low density and high strength/weight ratio making them ideal candidates for light-weight engineering applications.How-ever,magnesium and magnesium alloys are relatively reactive and tend to suffer severe corrosion during service [1,2].To increase the corrosion resistance and to improve the paint adhesion prop-erties of magnesium alloys,chemical conversion treatments are commonly applied to the surface.The properties of conversion coatings are closely related to their microstructure and compo-sitions,which in turn,strongly depend on the composition of the base magnesium alloys,the pre-treatment surface cleaning,the type and composition of the solution,and the corresponding operating parameters such as solution temperature and type and degree of agitation [3,4].The most popular and effective conver-sion process to produce a protective layer on the surface of metals is based on the immersion of the alloys in a bath containing chro-mate ions.The hexavalent chromium is reduced during corrosion to form an insoluble trivalent chromium species that terminates the oxidative attack [1].These coatings have been shown to pro-vide good corrosion protection for magnesium and its alloys in
?Corresponding author.Tel.:+8602368253884;fax:+8602368367675.E-mail addresses:liqingswu@https://www.wendangku.net/doc/ff14556316.html, ,akang420@https://www.wendangku.net/doc/ff14556316.html, ,chenbo11-1984@https://www.wendangku.net/doc/ff14556316.html, (Q.Li).
mild service conditions.However,the use of chromate baths is being progressively restricted due to the high toxicity of the hex-avalent chromium compounds.In order to avoid this drawback the new environmental-friendly pre-treatments such as stannate,rare earth salt and phosphate/permanganate conversion treatments have been actively developed in the recent decades [5–10].
Molybdates,tungstates,permanganates and vanadates,includ-ing similar chemical elements to chromium (groups VI and VII of the periodic table),were the ?rst chemicals tried as alternatives [11,12].Molybdenum is well known as a localized corrosion inhibitor when present in electrolyte as Mo (VI)or as an alloying element in steel [13].Because of the strong oxidation character,its reduction pro-duction is stabilization and can form a passive ?lm.Like chromate,molybdate acts as an oxidant in the chemical conversion treat-ments,its adsorbent production can inhibit the penetration of the inimical ions such as Cl ?to protect the substrate.
Molybdate treatments have been applied on Zn,Al alloy and steel substrates to improve the corrosion resistance of those sub-strates [14–16].Molybdate treatments have been also applied for decorative and solar absorption functional purposes [17].However,only few works are reported on the application of molybdate-based conversion coatings on magnesium alloys.The main problem which can arise when preparing molybdate-based coating on the magne-sium alloy substrate is the presence of pores and cracks what lead to serious deterioration of protective properties of pre-treatment layer.Therefore,in order to avoid this disadvantage,one of the measures is to prepare a sealing coating to cover on the pores and
0300-9440/$–see front matter ? 2009 Elsevier B.V. All rights reserved.doi:10.1016/j.porgcoat.2009.07.003
200J.Hu et al./Progress in Organic Coatings
66 (2009) 199–205
Fig.1.Flow chart of prior surface treatments and the composite coatings preparation.
cracks.Among the various coating techniques that are available for this purpose,a coating obtained with sol–gel method is of special interest especially in today’s environmental-protective society.Adhesion of sol–gel coatings to metal or metal oxide surfaces is especially favorable,because covalent bonds are formed between the substrate surface and the sol–gel ?lm.Various sol–gel proce-dures for magnesium were reported in the literatures [18–23].In this paper,a newly environmental-friendly composite anti-corrosion coatings technique was developed for AZ91D magnesium alloy to improve its corrosion resistance.The molybdate conver-sion coating,which acts as a barrier to environment,improved the corrosion resistance of the metal to some extent,then silicon sol–gel coating was deposited on the molybdate conversion coating through sol–gel technique to get a further improvement of corro-sion protection for magnesium alloy.Electrochemical techniques have been employed to characterize the corrosion properties of these coatings.2.Experimental 2.1.Materials
Die-caste AZ91D magnesium alloy with a chemical composition (wt.%)of Mg–8.77Al–0.74Zn was used in this study.Fig.1outlines the procedures for the mechanical and composite coatings treat-ment.
2.2.Molybdate conversion coating
The molybdate conversion coating was obtained by immersion of the samples in aerated 7.3g/L (NH 4)6Mo 7O 24·6H 2O aqueous solu-tion added with 8g/L KMnO 4and moderate amount of NaF additive at different temperatures (20,30and 50?C).Dipping times were
10,30and 60min,respectively.The pH of the molybdate bath was adjusted to 3and 5by phosphoric acid.After conversion,the sam-ples were rinsed in distilled water,and dried for 30min in oven at 60?C.
2.3.Silicon sol–gel coating
Silicon sol was prepared from tetraethylorthosilicate (TEOS),3-glycidoxypropyltrimethoxysilane (GPTMS)and ethanol,which were mixed in a molar ratio of 0.25:0.75:10,respectively,with the water being added dropwise into the mixture.Acetic acid was added to promote the hydrolysis reaction at 60?C,then ammonia was added to accelerate the condensation reaction after hydrolysis for 30min.The application of silicon sol–gel coating on the con-version coating was conducted by using a spin coating technique.Coated samples were cured in an oven at 100?C for 60min.2.4.Analysis and measurements
The Fourier transform infrared (FT-IR)spectrum recorded with IR-10300(PerkinElmer,America)has been carried out to analyze the structure of silicon xerogel prepared by silicon sol heat treat-ment at 100?C.
The potentiodynamic polarization curves were performed using a PS-268B system (Zhongfu,Beijing,China).A three-electrode cell,with the sample as the working electrode,a saturated calomel elec-trode (SCE)as reference and a platinum sheet as counter electrode,was employed in those tests.The area of the working electrode was 1.0cm 2.An aqueous solution of 3.5wt.%NaCl in which pH value was adjusted to 7with HCl or NaOH was used as elec-trolyte in the electrochemical measurements.After an initial delay of 10min in electrolyte,potentiodynamic polarization curves were scanned from ?1.7V at a rate of 1mV/s.The EIS measurements were
J.Hu et al./Progress in Organic Coatings66 (2009) 199–205
201
Fig.2.Potentiodynamic polarization curves in3.5wt.%NaCl solution.(a)The bare substrate.AZ91D magnesium alloy immersed in the molybdate conversion bath with pH3for(b)10min,(c)30min and(d)60min.
carried out using IM6e system(Co.Germany)in the frequency range of105Hz to50mHz.The signal amplitude was10mV.All samples were immersed for30min before impedance measurements.Elec-trochemical impedance spectrometry(EIS)data are presented as Nyquist plots and Bode plots.All of the tests were performed at room temperature.
The surface morphology of the molybdate conversion coating and the composite coatings was observed using images obtained from a scanning electron microscope(SEM)S-4800(HITACHI, Tokyo,Japan).The energy used for this analysis was20kV.
3.Results and discussion
3.1.Molybdate conversion coating
In order to obtain an effective protective molybdate coversion coating,it is an issue of prime importance for the investiga-tion of the optimal conversion parameters including the pH of the molybdate baths,immersion time and bath tempera-ture.Herein potentiodynamic polarization measurements were employed as a main technique for this investigation.The represen-tative potentiodynamic polarization curves for the samples treated by molybdate-based baths with pH3and5for different dipping times are presented in Figs.2and3,respectively.At the same time, the relevant electrochemical parameters calculated from the Tafel plots are also listed in Table1.The polarization resistance(R p)is determined from the slope of the voltage versus current density curve at the corrosion potential.In this paper,the potential for cal-culation of R p is chosen over a narrow voltage,from?10to+20mV relative to corrosion potential(E corr).Some relatively assumptions of linerarity have been given[24].
Corrosion current density(I corr),corrosion potential(E corr)and polarization resistance(R p)are often used to evaluate the corrosion protective property of the coatings.Based on these data,it is easy to draw a conclusion that the most effective protective molybdate conversion coating can be obtained in a solution pH5,immersion for30min.Additionally,the bath temperature did not have signif-icant effect on preparing the most effective protective molybdate conversion
coating.Fig.3.Potentiodynamic polarization curves tested in3.5wt.%NaCl solution.AZ91D magnesium alloy immersed in the molybdate conversion bath with pH5for(a) 10min,(b)30min and(c)60min.
We can discuss the in?uence of the bath pH on the corrosion protection of the molybdate conversion coating when the bath tem-perature and immersion time are treated as constants30?C and 30min,respectively.As is shown in Figs.2and3as well as Table1, it can be seen that the more corrosion resistive conversion coat-ings were obtained using baths with pH5in contrast to pH3.The E corr for the samples treated in the baths with pH3and5is?1.450 and?1.435V,respectively.And a lower I corr of the coating can be obtained from being treated in pH5solution compared with the case of pH3.
The immersion time also signi?cantly affected the protective abilities of the samples.The effect of immersion time in the molyb-date baths was prominent at pH5.In this case,the longer the time,the higher were the resistances.But after30min the situa-tion changed,longer immersion times in the baths produced a less protective?lm,as was evident from the reduction in the E corr and the increase in I corr recorded for the60min molybdate-treated elec-trode.Presumably,this is because the crack distribution is increased on the surface when for immersion time beyond30min,which was supported by images of SEM shown in Fig.4(c).So the best anti-corrosion molybdate conversion coating was achieved in the baths with pH5for30min.
The increase of the bath temperature from20to50?C did not have any signi?cant effect.The potentiodynamic polarization curves were not listed.Yang et al.[25]also demonstrated that the temperature of the vanadium-based chemical conversion coating on the corrosion resistance of magnesium alloy did not have obvious effect.
The SEM images shown in Fig.4are the morphologies of AZ91D magnesium alloy after immersion in molybdate bath for10,30and 60min.After10min of immersion in the conversion solution,the nucleation of the molybdate conversion coating was just started and coating thickness was not enough to completely cover the surface of the sample shown in Fig.4(a).Fig.4(b)displays the sur-face morphology of AZ91D magnesium alloy after the conversion coating treatment in the molybdate bath for about30min.It can be seen that the molybdate conversion coating presents network feature,and there were many micro-cracks on the surface of the coating.These cracks may be due to the release of hydrogen from
Table1
The electrochemical parameters of potentiodynamic polarization curves of pH5and3calculated from the Tafel plots.
pH3pH5
10min30min60min10min30min60min
E corr(mV/SCE)?1503?1450?1513?1510?1435?1480
I corr(A/cm2)17.4×10?59.0×10?514.4×10?5 4.0×10?5 1.76×10?5 3.8×10?5 R p( cm2)1142931505421230566
202J.Hu et al./Progress in Organic Coatings
66 (2009) 199–205
Fig.4.SEM images on AZ91D magnesium alloy in the solution of pH 5for (a)10min,(b)30min,(c)60min,(d)30min and silicon sol–gel coatings.
some chemical reaction such as the replacement reaction of Mg in acid solution during the conversion treatment and/or the dehydra-tion of the molybdate conversion coating after treatment.Similar phenomena can be seen in the rare earth conversion coatings and permanganate–phosphate conversion coatings [6]in magnesium alloy as well as molybdate conversion coatings in zinc galvanised steel [11].Fig.4(c)exhibits the surface morphology of AZ91D mag-nesium alloy after 60min immersion treatment in molybdate bath.It is obvious that the formation of cracks was more serious for longer immersion times than for shorter times’immersion.
In spite of the achievement for investigation the optimal param-eters of the most effective protective conversion coating has been obtained,the corrosion protection of this coating is really limited owing to the defects in the coating.Therefore,further treatment for enhancing the corrosion protection of the molybdate conversion coating is https://www.wendangku.net/doc/ff14556316.html,posite coatings
The composite coatings consisted of a conversion coating treated by molybdate bath with pH 5for 30min and three layers of silicon sol–gel coatings prepared by a spinning deposition technique.As a top coating of this composite coating,the three layers of silicon sol–gel coating play a very signi?cant role in improving the cor-rosion protection performance of AZ91D magnesium alloy,owing to the formation of a very stable,continuous,and highly adherent protective coating on the molybdate conversion coating.The sol was produced by a two-step process which includes hydrolysis via acid catalysis and condensation via base catalysis.As the crosslink-ing and assembling occurs upon application of the silicon sol on the prepared molybdate coating simultaneously with the evapora-tion of the solvent and coating formation leading to the composite coatings.
Fig.5shows the FT-IR spectra of the silicon xerogel and the sol precursors (TEOS and GPTMS).It is known that the Si–O–Si or Si–O has an asymmetric stretching mode in a wide https://www.wendangku.net/doc/ff14556316.html,parison of the IR spectra of the silicon xerogel,TEOS and GPTMS,silicon xerogel revealed a broad as (Si–O–Si)(1000–1110cm ?1),the as (Si–O)of the TEOS and GPTMS was present at 1081and 1088cm ?1,respectively.Besides,there was as (C–O–C)(1194cm ?1)in the FT-IR spectra of GPTMS and silicon xerogel.Based on the differences lied in hydroxyl groups infrared absorption band,it was evident that the co-condensation reaction between TEOS and GPTMS had occurred.For the silicon xerogel,the infrared absorption band of hydroxyl group appeared at 2939cm ?1,whereas the band at 2943and 2841cm ?1attributed to the presence of hydroxyl group in GPTMS.However,the hydroxyl group infrared absorption band is not found in the
TEOS.
Fig.5.The FT-IR spectrum of silicon xerogel,TEOS and GPTMS.
J.Hu et al./Progress in Organic Coatings66 (2009) 199–205
203
Fig.6.Potentiodynamic polarization curves for(a)the bare substrate,(b)the single conversion coating and(c)the composite coatings.
SEM image for the composite coatings is shown in Fig.4(d).It can be seen that the composite coatings is compact and imper-forate.It was expected that the composite coatings hold the best anti-corrosion ability for magnesium alloy.This observation was supported by the subsequent electrochemical measurement results.
In order to characterize the general corrosion properties of the composite coatings,the potentiodynamic polarization curves were recorded in the3.5wt.%NaCl solution.The representative polariza-tion curves for the composite coatings and the conversion coating are shown in Fig.6.In contrast to the substrate coated with a sin-gle conversion coating,the composite coatings exhibit lower I corr and higher E corr indicating that the composite coating has better corrosion protection performance compared with the single con-version coating.It demonstrates that the silicon sol–gel coatings can cover the pores and cracks on the molybdate conversion coat-ing in deed and offer a better corrosion protection performance. The relevant electrochemical parameters calculated from the Tafel plots are listed in Table2.
As is shown in Table2,compared with the bare substrate,the single conversion coating has a lower corrosion current density (I corr),higher corrosion potential(E corr)and larger polarization resistance(R p).While I corr for the composite coating is decreased approximately by two orders of magnitude,E corr is shifted posi-tively190mV and R p is increased by35-fold compared with the bare substrate,respectively.
The electrochemical impedance spectroscopy is one of the most intensively used and powerful techniques for the investigation and prediction of the anticorrosion protection[26].EIS was used in this work to estimate protective abilities of the conversion coating and the composite coatings on the AZ91D magnesium alloy in the 3.5wt.%NaCl aqueous solution.And EIS data for a freshly polished sample of AZ91D magnesium alloy with no coating was included as a comparison.
The low frequency impedance is one of the parameters which can be easily used to compare corrosion protection performance of different systems.Higher impedance demonstrates better protec-tion[26].As shown in Fig.7,the bare substrate showed the poorest corrosion resistance after30min of immersion in the3.5wt.%NaCl aqueous solution.In the low frequency region,it can be seen that the impedance drops as the frequency drops,indicating that the surface
Table2
The electrochemical parameters of potentiodynamic polarization curves calculated from the Tafel plots.
E corr
(mV/SCE)I corr(A/cm2)R p( cm2)
The substrate?1614.0 1.29×10?51685.20 The conversion coating?1435.6 1.76×10?51230.46 The composite coatings?1425.5 3.80×10?758,692.10Fig.7.EIS Bode plots obtained in3.5wt.%NaCl solution for(a)the bare substrate, (b)the single conversion coating and(c)the composite coatings.
oxide layer of the bare substrate formed in air is not protective[27]. For samples of the conversion coating and the composite coatings, the low frequency impedance in Bode plot continues to increase as the frequency drops,indicating a strong resistance to the?ow of ions and electrons by the coatings,hence preventing corrosion. Especially,the composite coatings increase the impedance further by at least two orders of magnitude compared with the bare sub-strate.The same effects on corrosion resistance can be observed in Nyquist plot(Fig.8).The surface resistance of composite coatings was about4.5×104 cm2,which is equal to75times the resis-tance of bare substrate.Thus,it demonstrates that the composite coatings serve as a considerably effective barrier against corrosion electrolyte ingress during EIS measurement.
For quantitative estimation of the corrosion protection,exper-imental impedance
spectra were?tted using equivalent circuits. The impedance spectroscopy of the conversion coating was mod-eled using the scheme shown in Fig.9(a).Here,constant phase elements were used instead of capacitances in order to take account of the dispersive character of the time constants originat-
Fig.8.EIS Nyquist plots obtained3.5wt.%NaCl solution for(1):(a)the bare substrate and(b)conversion coating,(2)the composite coatings.
204J.Hu et al./Progress in Organic Coatings 66 (2009) 199–205
Table 3
The main ?tting parameters for EIS data obtained for the conversion coating and the composite coatings.
R inter
( cm 2)
R conv ( cm 2)R sol (
cm 2)R polar ( cm 2)C dl (F/cm 2)Conversion coating 39.91366.0–552.9 5.03×10?4Composite coatings
138.9
1032.0
16,720.0
29,260.0
2.98×10?7
Fig.9.The conversion coating equivalent circuit (a)and (b)the ?tting result.
Fig.10.The composite coatings equivalent circuit (a)and (b)the ?tting result.
ing from the nonuniformity of the coatings.R solt is the resistance of solution;R inter and Q inter refer to the resistance and the capac-itance of solution/coating interface,respectively;R conv and Q conv represent the resistance of conversion coating,respectively.The presence of several pores and cracks is on the conversion coating,in which penetration of active chloride ions and water leads to par-tial destruction.With the development of the corrosion process,the polarization resistance R polar and double layer capacitance C dl should be added in the ?tting circuit due to the appearance of a new time constant in the low frequency region.The corresponding equivalent circuit for the EIS of the composite coatings is shown in Fig.10(a).Compared with the ?tting circuit of conversion coating,R sol and Q sol representing the resistance and capacitance of sol–gel coating,respectively,are added to this one due to the deposition of silicon coatings on the conversion coating.
Based on the main parameters for EIS data obtained for the both coatings listed in Table 3,a great improvement on corro-sion resistance of the substrate has been obtained owing to the contribution of composite coatings with a high coating resistance (R =R inter +R sol +R conv +R polar ).Namely,the composite coatings act as a good barrier for the penetration of active chloride ions and water,subsequently enhancing the anticorrosion performance of the AZ91D magnesium alloy.C dl of the composite coatings sample shows almost a very low value (2.98×10?7F/cm 2)demonstrates excellent protective properties even the absence of active defects at substrate/coating interface.
4.Conclusions
Composite anti-corrosion coatings for AZ91D magnesium alloy has been evaluated in this work.The ?rst coating is molybdate con-version coating,while the second is three layers of silicon sol–gel coatings (applied by spin coating technique after the deposition molybdate conversion coating on AZ91D magnesium alloy).
The molybdate conversion coating (7.3g/L (NH 4)6Mo 7O 24·6H 2O solution with pH 5for 30min at 30?C)provides higher corrosion potential alloy but a lower corrosion current density to the AZ91D magnesium alloy as indicated by electrochemical measurements carried out at room temperature.The molybdate conversion coating presents network feature,and plenty of micro-cracks exists on the surface of the coating observed by SEM image.
The three layers of silicon sol–gel coatings can totally cover the cracks produced on the molybdate conversion coating as can be seen from the SEM image.It can explain why the composite coat-ings hold the best corrosion resistant compared with the single conversion coating and the bare substrate.Acknowledgements
The authors thank the supports of the Natural Science Foun-dation of Chongqing,China (CSTC.2005BB4055)and High-Tech Cultivation Program of Southwest Normal University (No.XSGX06).References
[1]J.E.Gray,B.Luan,J.Alloys Compd.336(2002)88–113.
[2]M.An?k,E.K?rpe,Surf.Coat.Technol.201(2007)4702–4710.[3]C.S.Lin,H.C.Lin,K.M.Lin,https://www.wendangku.net/doc/ff14556316.html,i,Corros.Sci.48(2006)93–109.
[4]
K.Brunelli,M.Dabalà,I.Calliari,M.Magrini,Corros.Sci.47(2005)989–1000.
J.Hu et al./Progress in Organic Coatings66 (2009) 199–205205
[5]H.H.Elsentriecy,K.Azumi,H.Konno,Surf.Coat.Technol.202(2007)532–537.
[6]K.Z.Chong,T.S.Shih,Mater.Chem.Phys.80(2003)191–200.
[7]A.L.Rudd,C.B.Breslin,Florian Mansfeld.Corros.Sci.42(2000)275–288.
[8]T.Takenaka,T.Ono,Y.Narazaki,Y.Naka,M.Kawakami,Electrochim.Acta53
(2007)117–121.
[9]F.Zucchi,A.Frignani,V.Grassi,G.Trabanelli,C.Monticelli,Corros.Sci.49(2007)
4542–4552.
[10]F.H.Scholes,C.Soste,A.E.Hughes,S.G.Hardin,P.R.Curtis,Appl.Surf.Sci.253
(2006)1770–1780.
[11]E.Almeida,T.C.Diamantino,M.O.Figueiredo,C.Sá,Surf.Coat.Technol.106
(1998)8–17.
[12]E.Almeida,L.Fedrizzi,T.C.Diamantino,Surf.Coat.Technol.105(2007)97–101.
[13]A.A.O.Magalhˇa es,I.C.P.Margarit,O.R.MAttos,J.Electroanal.Chem.572(2004)
433–440.
[14]K.Kurosawa,T.Fukushima,Corros.Sci.29(1989)1103–1114.
[15]J.D.Wilcox,D.R.Gabe,M.E.Warwick,Corros.Sci.28(1988)577–585.
[16]H.Konno,K.Narumi,H.Habazaki,Corros.Sci.44(2002)1889–1900.[17]A.A.O.Magalh?es,I.C.P.Margarit,O.R.Mattos,J.Electroanal.Chem.572(2004)
433–440.
[18]A.L.K.Tan,A.M.Soutar,I.F.Annergren,Y.N.Liu,Surf.Coat.Technol.198(2005)
478–482.
[19]A.R.Phain,F.J.Gammel,T.Hack,Surf.Coat.Technol.201(2006)3299–3306.
[20]A.R.Phain,F.J.Gammel,T.Hack,H.Haefke,Mater.Corros.56(2005)77–83.
[21]J.Hu,Q.Li,X.Zhong,https://www.wendangku.net/doc/ff14556316.html,.Coat.63(2008)13–17.
[22]Q.Li,X.Zhong,J.Hu,https://www.wendangku.net/doc/ff14556316.html,.Coat.63(2008)222–227.
[23]X.Zhong,Q.Li,J.Hu,Corros.Sci.50(2008)2304–2309.
[24]F.Manseld,Corros.Sci.47(2005)3178–3186.
[25]K.H.Yang,M.D.Ger,W.H.Hwu,Y.Sung,Y.C.Liu,Mater.Chem.Phys.101(2007)
480–485.
[26]https://www.wendangku.net/doc/ff14556316.html,maka,M.L.Zheludkevich,K.A.Yasakau,R.Serra,S.K.Poznyak,M.G.S.
Ferreira,https://www.wendangku.net/doc/ff14556316.html,.Coat.58(2007)127–135.
[27]D.F.Roeper,D.Chidambaram,.R.Clayton,G.P.Halada,Electrochim.Acta53
(2008)2130–2134.
神通数据库参数配置工具手册
神通数据库 参数配置工具手册 版本6.0 天津神舟通用技术有限公司 2010年1月
版权声明 神通数据库是天津神舟通用技术有限公司开发的数据库管理系统软件产品。神通数据库的版权归天津神舟通用技术有限公司，任何侵犯版权的行为将追究法律责任。 《神通数据库SQL语言参考手册》的版权归天津神舟通用技术有限公司所有。 未经天津神舟通用技术有限公司的书面准许，不得将本手册的任何部分以任何形式、采用任何手段(电子的或机械的，包括照相复制或录制)、或为任何目的，进行复制或扩散。 (c)Copyright 2010 天津神舟通用技术有限公司。版权所有，翻制必究。 天津神舟通用技术有限公司不对因为使用该软件、用户手册或由于该软件、用户手册中的缺陷所造成的任何损失负责。
阅读指南 〖阅读对象〗 本手册是为使用神通数据库管理系统的用户编写的。使用神通数据库的用户在安装神通数据库之前应当认真阅读本手册，以便熟悉安装程序的使用，进行神通数据库管理系统的安装。 〖内容简介〗 本手册介绍了如何使用神通数据库系统参数配置工具对神通数据库运行参数进行配置，目的是让用户该工具有一个全面的了解，方便用户配置神通数据库参数。 神通数据库系统参数配置工具采用Java语言编写，具有跨平台性，可以在Windows 、Linux 等多种系统平台上运行，用户在一个操作系统平台上熟悉了该工具的使用后，可以很容易的在其他系统平台上使用该工具。 〖相关文档〗 使用本手册时可以参考神通数据库的手册集，手册集包含以下文档： 《神通数据库安装手册》 《神通数据库备份恢复工具使用手册》 《神通数据库DBA管理工具使用手册》 《神通数据库系统管理员手册》 《神通数据库嵌入式SQL语言手册》 《神通数据库交互式SQL查询工具使用手册》 《神通数据库JDBC开发指南》 《神通数据库过程语言手册》 《神通数据库OLEDB/ADO用户手册》 《神通数据库迁移工具使用手册》 《神通数据库ODBC程序员开发指南》 《神通数据库审计管理》 《神通数据库审计工具使用手册》 《神通数据库性能监测工具使用手册》 《神通数据库作业调度工具使用手册》 〖手册约定〗 本手册遵循以下约定： 所有标题均使用黑体字。 如果标题后跟有“【条件】”字样，说明该标题下正文所要求的内容只是在一定条件下必须的。 【注意】的意思是请读者注意那些需要注意的事项。 【警告】的意思是请读者千万注意某些事项，否则将造成严重错误。 【提示】的意思是提供给读者一些实用的操作技巧。
ORACLE数据库管理初始化参数
管理初始化参数 管理初始化参数（调优的一个重要知识点，凭什么可以对数据库进行调优呢？是因为它可以对数据库的一些参数进行修改修正） 初始化参数用于设置实例或是数据库的特征。oracle9i提供了200多个初始化参数，并且每个初始化参数都有默认值。 显示初始化参数(1) show parameter命令 如何修改参数需要说明的如果你希望修改这些初始化的参数，可以到文件D:\oracle\admin\myoral\pfile\init.ora文件中去修改比如要修改实例的名字数据库（表）的逻辑备份与恢复 逻辑备份是指使用工具export将数据对象的结构和数据导出到文件的过程，逻辑恢复是指当数据库对象被误操作而损坏后使用工具import利用备份的文件把数据对象导入到数据库的过程。 物理备份即可在数据库open的状态下进行也可在关闭数据库后进行，但是逻辑备份和恢复只能在open的状态下进行。 导出导出具体的分为：导出表，导出方案，导出数据库三种方式。 导出使用exp命令来完成的，该命令常用的选项有： userid：用于指定执行导出操作的用户名，口令，连接字符串 tables：用于指定执行导出操作的表 owner：用于指定执行导出操作的方案 full=y：用于指定执行导出操作的数据库 inctype：用于指定执行导出操作的增量类型 rows：用于指定执行导出操作是否要导出表中的数据 file：用于指定导出文件名 导出表 1.导出自己的表exp userid=scott/tiger@myoral tables=(emp,dept) file=d:\e1.dmp 2.导出其它方案的表如果用户要导出其它方案的表，则需要dba的权限或是exp_full_database的权限，比如system就可以导出scott的表E:\oracle\ora92\bin>exp userid=system/manager@myoral tables=(scott.emp) file=d:\e2.emp 特别说明：在导入和导出的时候，要到oracle目录的bin目录下。 3. 导出表的结构exp userid=scott/tiger@accp tables=(emp) file=d:\e3.dmp rows=n 4. 使用直接导出方式exp userid=scott/tiger@accp tables=(emp) file=d:\e4.dmp direct=y 这种方式比默认的常规方式速度要快，当数据量大时，可以考虑使用这样的方法。 这时需要数据库的字符集要与客户端字符集完全一致，否则会报错... 导出数据库导出数据库是指利用export导出所有数据库中的对象及数据，要求该用户具有dba的权限或者是exp_full_database权限 增量备份（好处是第一次备份后，第二次备份就快很多了） exp userid=system/manager@myorcl full=y inctype=complete file=d:\all.dmp
用友NC数据库服务器参数配置说明
数据库服务器参数配置说明目录 DB2的参数配置说明 数据库环境变量配置 2CPU，2G内存配置建议 4CPU，4G内存配置建议 8CPU，8G内存配置建议 ORACLE的参数配置说明 公共参数（适用于所有硬件配置） 2CPU，2G内存配置建议 4CPU，4G内存，32位数据库配置建议 4CPU，4G内存，64位数据库配置建议 8CPU，8G内存配置建议 SQL Server数据库配置建议 DB2的参数配置说明 下面参数是针对NC应用建议性调整，具体需要根据应用规模和特点再调整 数据库环境变量设置 db2set DB2_SKIPINSERTED=YES db2set DB2_INLIST_TO_NLJN=YES db2set DB2_MINIMIZE_LISTPREFETCH=YES db2set DB2_ANTIJOIN=EXTEND 2CPU，2G内存配置建议 系统大约支持用户并发数：30左右
数据库管理器配置参数 --1.应用程序支持层堆大小(aslheapsz) (4K) update dbm cfg using aslheapsz 256; --2.排序堆阈值(sheapthres) (4K) update dbm cfg using sheapthres 20000 ; --3.代理程序的最大数目(maxagents) update dbm cfg using maxagents 100; --4.代理程序池大小(NUM_POOLAGENTS) update dbm cfg using NUM_POOLAGENTS 30; 数据库配置参数 假设NC数据库名称为“ncdata00” --1.数据库堆(DBHEAP)(4K) update database configuration for ncdata00 using DBHEAP 4096 automatic; --2.日志缓冲区大小(logbufsz) (4K) update database configuration for ncdata00 using logbufsz 512 automatic; --3.编目高速缓存大小(CATALOGCACHE_SZ) (4K) update database configuration for ncdata00 using CATALOGCACHE_SZ 1024 automatic; --4.用于锁定列表的最大内存(locklist) (4K) update database configuration for ncdata00 using locklist 4096 automatic; --5.最大应用程序控制堆大小(app_ctl_heap_sz) (4K) -- update database configuration for ncdata00 using app_ctl_heap_sz 2048; update database configuration for ncdata00 using appl_memory automatic; --6.排序堆大小(sortheap)(4K) update database configuration for ncdata00 using sortheap 2048 automatic; --7.语句堆大小(stmtheap) (4K) update database configuration for ncdata00 using stmtheap 2048 automatic; --8.应用程序堆大小(applheapsz)(4K) update database configuration for ncdata00 using applheapsz 1024 automatic;
数据库调优参数配置以及参数说明
数据库参数配置 参数说明 1．maxagents －最大代理程序数配置参数 从版本9.5 起，就不推荐使用此参数。数据库管理器将忽略对此配置参数指定的任何值。 此参数指示可在任何给定时间接受应用程序请求的数据库管理器代理程序（无论是协调代理程序还是子代理程序）的最大数目。 配置类型 数据库管理器 适用于 ?带有本地和远程客户机的数据库服务器 ?带有本地客户机的数据库服务器 ?带有本地和远程客户机的分区数据库服务器
参数类型 可配置 缺省值[范围] 200 [1 - 64 000] 在带有本地和远程客户机的分区数据库服务器上为400? [1 - 64 000] 计量单位 计数器 如果您想限制协调代理程序数，请使用max_coordagents参数。 此参数可在内存受约束的环境中来限制数据库管理器使用的内存总量，因为每个附加 代理程序都需要附加内存。 建议：maxagents的值至少应为每个数据库中允许同时访问的maxappls的值之和。 如果数据库数大于numdb参数，那么最安全的过程是使用具有maxappls的最大值 的numdb产品。 每个附加代理程序都需要一些在数据库管理器启动时分配的资源开销。 如果在尝试连接至数据库时遇到内存错误，请尝试进行下列配置调整： ?在未启用查询内并行性的非分区数据库环境中，增大maxagents数据库配置参数的值。 ?在分区数据库环境或启用了查询内并行性的环境中，增大maxagents或 max_coordagents中较大者的值。 2. num_poolagents －代理程序池大小配置参数 此参数设置空闲代理程序池的最大大小。 配置类型 数据库管理器 适用于 ?带有本地和远程客户机的数据库服务器 ?带有本地客户机的数据库服务器 ?带有本地和远程客户机的分区数据库服务器 参数类型 可联机配置 缺省值
PostgreSQL数据库配置参数详解
十章数据库参数 PostgresSQL提供了许多数据库配置参数，本章将介绍每个参数的作用和如何配置每一个参数。 10.1 如何设置数据库参数 所有的参数的名称都是不区分大小写的。每个参数的取值是布尔型、整型、浮点型和字符串型这四种类型中的一个，分别用boolean、integer、floating point和string表示。布尔型的值可以写成ON、OFF、TRUE、FALSE、YES、NO、1和0，而且不区分大小写。 有些参数用来配置内存大小和时间值。内存大小的单位可以是KB、MB和GB。时间的单位可以是毫秒、秒、分钟、小时和天。用ms表示毫秒，用s表示秒，用min表示分钟，用h表示小时，用d表示天。表示内存大小和时间值的参数参数都有一个默认的单位，如果用户在设置参数的值时没有指定单位，则以参数默认的单位为准。例如，参数shared_buffers 表示数据缓冲区的大小，它的默认单位是数据块的个数，如果把它的值设成8，因为每个数据块的大小是8KB，则数据缓冲区的大小是8*8=64KB，如果将它的值设成128MB，则数据缓冲区的大小是128MB。参数vacuum_cost_delay 的默认单位是毫秒，如果把它的值设成10，则它的值是10毫秒，如果把它的值设成100s，则它的值是100秒。 所有的参数都放在文件postgresql.conf中，下面是一个文件实例: #这是注释 log_connections = yes log_destination = 'syslog' search_path = '"$user", public' 每一行只能指定一个参数，空格和空白行都会被忽略。“ #”表示注释，注释信息不用单独占一行，可以出现在配置文件的任何地方。如果参数的值不是简单的标识符和数字，应该用单引号引起来。如果参数的值中有单引号，应该写两个单引号，或者在单引号前面加一个反斜杠。 一个配置文件也可以包含其它配置文件，使用include指令能够达到这个目的，例如，假设postgresql.conf文件中有下面一行： include ‘my.confg’
数据库的建库基本知识
数据库培训之建库基本知识 一.数据库创建初期应该注意的知识 1.如何创建表空间 create tablespace OEM_REPOSITORY datafile'D:\Oracle\oracleR2\zhtd\OEM_REPOSITORY_01.dbf' size50m autoextend on next10m extent management local online; ?指明路径（需要注意所向的磁盘空间是否足够）； ?定义初始化大小，以及自动增长率； ?指定其有本地表空间（本地表空间的好处是能自己分配空闲表空间到业务繁忙的表空间，降低由于Delete引起的表空间碎片产生的影响）； ?指定其为在线状态，如果是offline的话，ORACLE 是无法访问其内容的； ?通常情况下，按以上方法指定的表空间，是不必要给太大的初始化值的，因为已经指定了该表空间自动增长。 2.如何创建用户 create user GZPWMIS identified by "bcc" default tablespace TS_PWSC temporary tablespace TEMP profile DEFAULT; grant connect to GZPWMIS; grant dba to GZPWMIS; grant resource to GZPWMIS; grant unlimited tablespace to GZPWMIS; ?在定义时就给用户设置密码； ?指定该用户所在的表空间和临时表空间； ?给用户赋权 ?指定用户可能使用到表空间的大小（本例是无限） 3.如何创建表 create table CORE_ROLE ( rolecode NUMBER not null, orgcode VARCHAR2(50), rolename VARCHAR2(50) ) tablespace TS_PWSC pctfree10 initrans1 maxtrans255 storage
数据库常见错误及参数设置
话单工具数据库常见错误及参数设置 错误1. 解决方法：话单文件中的DownLinkVolume_B字段类型和数据库中的该字段类型不匹配，导致导入错误，在我们的新话单工具中对这种错误是把该话单文件作为错误话单，抛弃整个话单文件，放入badCDR文件中。 错误2： 解决方法：也是话单文件中的数据类型不正确导致入库错误，在新话单导入工具中是默认选
择 1.stop ，保证在后台不会出现大量的select an option.和县招聘https://www.wendangku.net/doc/ff14556316.html,/post/job/ 错误3： 解决方法：连接数据库错误，查看话单工具中的配置文件，服务器所在网络的通畅，数据库是否开启。 错误4： /19 11:06:20. 0000000003 [20152]: You have run out of IQ STORE dbspace in database /home/sybase/yrg/yrg.db. In another session, please issue a CREATE DBSPACE ... IQ STORE command and add a dbspace of at least 8 MB. 解决方法：数据库的临时表空间不足，导致报错，我们要加大临时表空间的大小，执行以下语句 CREATE DBSPACE new_temp AS '/home/sybase/yrg/newiq.iqtmp' IQ TEMPORARY STORE size 1000 reserve 500; 上面的路径，增加空间大小和保留空间大小可以按照现场数据库和需要来定义。 错误5： 解决方法：数据库参数query_temp_space_limit设置不合理，解决该问题，要执行以下命令Set option query_temp_space_limit=0; Commit; 问题6： 在新建数据库中，要配置数据库按照目录下的.Cfg文件中的两个参数，如下：
数据库内容技术参数基本情况
数据库内容、技术参数基本情况 1.银符考试模拟题库 银符考试数据库：主要购买其中计算机类、法律类、公务员类、经济类、工程类、综合类、研究生类各种等级考试历年真题及模拟题。此数据库主要针对学生考试所需。 2.畅想之星光盘数据库 畅想之星非书资源管理平台，是针对图书馆的非书资料管理的平台，主要是针对随书光盘进行高效地管理和利用。数据库主要针对教师、学生对图书馆随书光盘利用所购。 3.爱迪科森网上报告厅 系统平台：
4.读秀学术搜索 包括：整合馆藏纸书、电子资源数据库；深度检索（全文检索、目录检索等）；图书原文显示，检索结果中图书可以显示17页原文（封面页、前言页、目次页、版权页、正文17页等），全文检索可显示检索点起的10页原文，文献传递服务；免费文献传递服务，参考咨询服务中心提供的局部使用，提供图书单次不超过50页、单篇文章（6页）的文献传递，同本文献一周累计咨询量不超过整本的20% ，所有文献咨询有效期为1个月；整合外文数据库，实现中外文的统一检索；一千万篇报纸、500万篇文档。 5.国道外文数据库 购买 6 个专题库赠送 2个专题库数据库：外文国外生物技术专题数据库；外文国外建筑工程专题数据库；外文国外化学专题数据库；外文国外环境专题数据库（赠送）；外文国外能源专题数据库；外文国外材料专题数据库；外文国外测绘科学专题数据库；外文国外交通运输工程专题数据库（赠送） 6.新东方多媒体数据库 技术参数：
7.妙思图书馆管理系统 软件升级售后服务费 8.ASCE美国土木工程协会数据库 美国土木工程师学会是全球最大的土木工程全文文献资料库。它收录了ASCE所有专业期刊（回溯至1983年）和会议录（回溯至2000年），总计超过73,000篇全文、650,000页资料；每年新增约4,000篇文献。ASCE出版的期刊大部分被SCI收录，其中，有11本期刊在2009年JCR收录106本土木工程类期刊中，总引用量排名前40名。ASCE每年有5万多页的出版物。土木工程是我校的招牌专业，此数据库为教学科研所需。 9.超星移动图书馆
数据库job的启用及参数设置
数据库job的启用及参数设置 2010-07-06 20:20:36| 分类：oracle | 标签： |举报 |字号大中小订阅 众所周知，一般操作系统会提供定时执行任务的方法，例如：Unix平台上提供了让系统定时执行任务的命令Crontab。但是，对于某些需求，例如：一些对数据库表的操作，最为典型的是证券交易所每日收盘后的结算，它涉及大量的数据库表操作，如果仍然利用操作系统去定时执行，不仅需要大量的编程工作，而且还会出现用户不一致等运行错误，甚至导致程序无法执行。 一、分析问题 事实上，对于以上需求，我们可以利用数据库本身拥有的功能Job Queue（任务队列管理器）去实现。任务队列管理器允许用户提前调度和安排某一任务，使其能在指定的时间点或时间段内自动执行一次或多次，由于任务在数据库中被执行，所以执行效率很高。 任务队列管理器允许我们定制任务的执行时间，并提供了灵活的处理方式，还可以通过配置，安排任务在系统用户访问量少的时段内执行，极大地提高了工作效率。例如，对于数据库日常的备份、更新、删除和复制等耗时长、重复性强的工作，我们就可以利用任务队列管理器去自动执行以减少工作量。 目前，拥有此项功能的数据库有许多，最有代表性的是SQL Server 7.0、Oracle 8.0.5等。但是，要让任务队列管理器工作，还需要我们加以配置才能实现。SQL Server的功能配置是在一个图形化界面（GUI）中实现的，非常简单。利用OEM客户端管理工具，Oracle的配置也可以在一个图形界面中完成。然而大多数的用户更习惯于命令行的方式去操纵数据库。本文介绍如何通过命令行实现这种配置。 二、实现步骤 1．确保Oracle的工作模式允许启动任务队列管理器 Oracle定时执行“Job Queue”的后台程序是SNP进程，而要启动SNP进程，首先要确保整个系统的模式是可以启动SNP进程的，这需要以DBA的身份去执行如下命令： svrmgrl> alter system enable restricted session; 或sql> alter system disenable restricted session; 利用如上命令更改系统的会话方式为disenable restricted，为SNP的启动创造条件。 2．确保Oracle的系统已经配置了任务队列管理器的启动参数 SNP的启动参数位于Oracle的初始化文件中，该文件放在＄ORACLE_HOME/dbs路径下，如果Oracle的SID是myora8的话，则初始化文件就是initmyora8.ora，在文件中对SNP启动参数的描述部分如下： job_queue_process=n job_queue_interval=N 第一行定义SNP进程的启动个数为n。系统缺省值为0，正常定义范围为0～36，根据任务的多少，可以配置不同的数值。 第二行定义系统每隔N秒唤醒该进程一次。系统缺省值为60秒，正常范围为1～3600秒。事实上，该进程执行完当前任务后，就进入睡眠状态，睡眠一段时间后，由系统的总控负责将其唤醒。 如果该文件中没有上面两行，请按照如上配置添加。配置完成后，需要重新启动数据库，使其生效。注意：如果任务要求执行的间隔很短的话，N的配置也要相应地小一点。 3．将任务加入到数据库的任务队列中 调用Oracle的dbms_job包中的存储过程，将任务加入到任务队列中： dbms_job.submit( job out binary_integer, what in archar2, next_date in date， interval in varchar2, no_parse in boolean) 其中： ●job：输出变量，是此任务在任务队列中的编号； ●what：执行的任务的名称及其输入参数； ●next_date：任务执行的时间；
SQL动态参数操作数据库及报表设计
第八次实验：SQL动态参数操作数据库及报表设计 一、实验目的： 1. 熟练掌握数据库组件AdoQuery的连接操作； 2. 熟悉Delphi制作完成数据库SQL中Select命令完成查找操作的应用程序； 3. 熟悉数据库的SQL中：修改、添加、删除； 4. 掌握动态参数操作数据库； 5. 掌握制作数据报表。 二、实验内容： 1. 完成Delphi制作的学生的宿舍信息应用程序中的Select查找； 2. 完成Insert、Update、Delete的SQL命令操作； 3. 完成动态参数的设制并制作主/明细表的应用操作程序； 4. 学习应用QuickRep组件完成数据库报表。 三、实验步骤 1.连接数据库MicroSoft表到Delphi的程序中， 1）. 分析学生宿舍信息包含的结构内容： 2）. 建立关系数据库结构： 3）. 利用MicroSoft Access 建立该表 4）.连接数据库： 1〉adoQuery 2〉DataSource 3〉DBgrid 4）. 查询男生信息 AdoQuery1. close；
Adoquery1.SQL . clear； AdoQuery1. SQL . Add（‘Select * from XX表 Where 性别= ’+edit1.text{‘男’}）Adoquery1.SQL.open； 2. 完成数据库的修改，添加，删除操作： 1）. 将工程文件打开（可以使用以往的程序架构）； 2）. 添加组件： Panel 面板一个；MainMenu菜单一个；文本显示框多个；AdoTable，Datasource，DBgrid，DBtext连接组建多个； 按钮组建多个。 3）. 修改属性： 4）. 添加功能代码 a> 修改： …………………… AdoQuery1. SQL . Add（‘Update XX表 Set xx字段=值 Where 性别= ’+edit1.text{‘男’}） …………………… b> 添加： …………………… AdoQuery1. SQL . Add（‘Insert Into XX表（xx字段……） Valuse（xx字段的值……）） …………………… c> 删除： …………………… AdoQuery1. SQL . Add（‘Delete From XX表 Where 性别= ’+edit1.text{‘男’}）…………………… 3.学习应用AdoQuery组件操作Select命令完成数据库动态查询的主明细表操作。 制作一张宿舍结构表、班级信息表； 1）. 将工程文件打开（可以使用以往的程序架构）；
数据库企业版-招标参数
数据库企业版 1、授权具有永久使用权 2、支持各个主流厂商的硬件及操作系统平台，Unix, Linux, Windows。转换平台时，应用程序不用修改。 3、支持主流的网络协议，（如：TCP/IP、IPX/SPX、NETbios 及混合协议）。 4、支持多CPU SMP平台，支持基于共享存储的并行集群。 5、支持存储关系型数据和对象型数据。 6、具有支持并行操作所需的技术，包括多CPU并行和多服务器并行、事务处理的完整性控制技术等，支持并行查询/DML、备份/恢复、导入/导出、索引创建。 7、DML操作只能有行级锁，任何情况下不允许有锁定过多资源的锁升级，以降低死锁的可能性，若出现死锁，能自动解锁。 8、多个用户操作同一条记录时，任何情况下读、写互不影响，并且不能有读取其他用户未提交数据的脏读。 9、支持同构、异构数据源的访问，包括文件数据源；能和异构数据库互相复制。 10、支持存储过程、触发器。触发器支持语句执行前、执行后和可替换型三种方式。支持行级触发器。触发器的触发操作和事件包括DML、DDL、数据库启停、错误信息、登录/注销。 11、支持B1级安全标准，内嵌行级安全功能，支持基于行业标准的数据库存储加密、传输加密及完整性校验。支持增强的密码安全性，支持区分大小写、多字节密码和强壮的密码散列算法，例如安全散列算法 (SHA-1)。 12、支持在一台机器的浏览器界面中统一管理不同平台的多个数据库。 13、能够将原有异种数据库向本数据库无损失移植。 14、支持中文国标字符集等多字节字符集，支持Unicode 3.2以上版本。 15、应具有强的容错能力、错误恢复能力、错误记录及预警能力，能在不影响数据库运行的条件下快速恢复已提交的修改，可以把整个数据库、指定表或指定的记录恢复到指定时间点。 16、数据库、表大小等参数可在线设置，支持在线重建索引。 17、内嵌对多媒体、医学成像及地理信息数据的支持。支持新的Java高级图像(JAI)标准。
怎么查看数据库参数配置信息上岗前准备
怎么查看数据库参数配置信息-上岗前准备 正式上岗前的准备：怎么查看数据库参数配置信息 个人分类：oracle 做性能测试实际上是一个不短调优和测试的过程，而不是一次测试结束就完成了那么简单，中间分析调优的过程至关重要，接触oracle 也有很长时间了，我们开发使用的数据库都是使用oracle的，也一直没有对oracle做总结，这里写这篇文章也算是自己学习和总结吧。下面就开始吧，不对之处还望指正，有些是摘自学习从书上拿来，有些查到的资料收集，也有一些自己的心的。 1、安装时注意：选择企业数据库中的一般用途 2、专用服务器与共享服务器的区别：在专用连接中，连接所需要的资源全部在PGA中分配。该内存区为指定连接私有，其它进：程不能访问。专用连接采用一对一的连接方式，能很快的响应用户的请求，
但是，如果连接用户太多时，由于要对每一个连接分配资源，因此，连接数受硬件限制比较大。为了克服这种情况，Oracle提出了共享连接的连接方法，即用一个服务器的进程响应多个用户连接，与专用连接不同有连接时才创建PGA不同，共享连接在实例一启动，就分配指定数量的服务器进程，所用户的连接，以排队的方式，由分配器指定给服务器进程，其它的进程排队等待。只要用户的请求一执行完，就会马上断开连接，分配器会把空闲的服务器进程分配给其它排除的进程。 长事务的共享连接会造成shared server进程的严重排队，造成性能的严重下降，长事务采用专用模式 在短事务多用户并发的情况下，多用Oracle的共享模式提高数据库性能，提高访问速度。web服务都是采用这样的服务模式来提高系统的并发性能，如果你的是j2ee或者.net的web服务都是需要采用这样的服务模式，具体配置过程你可以查手册。。。 3、配置成功验证方法： 查看共享配置成功的方式：
各种数据库JDBC参数配置
各种数据库JDBC参数配置 博客分类： 数据库 各种数据库JDBC参数配置 MySQL： String Driver="com.mysql.jdbc.Driver" ; //驱动程序 String URL="jdbc:mysql://localhost:3306/db_name" ; //连接的URL,db_name为数据库名 String Username="username" ; //用户名 String Password="password" ; //密码 Class.forName(Driver).new Instance(); Connection con=DriverManager.getConnection(URL,Username,Password); Microsoft SQL Server 2.0 驱动( 3 个jar的那个): String Driver="com.microsoft.jdbc.sqlserver.SQLServerDriver" ; //连接SQL数据库的方法String URL="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=db_name" ; //db_name为数据库名 String Username="username" ; //用户名 String Password="password" ; //密码 Class.forName(Driver).new Instance(); //加载数据可驱动 Connection con=DriverManager.getConnection(URL,UserName,Password); // Microsoft SQL Server 3.0 驱动( 1 个jar的那个): // 老紫竹完善 String Driver="com.microsoft.sqlserver.jdbc.SQLServerDriver" ; //连接SQL数据库的方法String URL="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=db_name" ; //db_name为数据库名 String Username="username" ; //用户名 String Password="password" ; //密码 Class.forName(Driver).new Instance(); //加载数据可驱动 Connection con=DriverManager.getConnection(URL,UserName,Password); //